Cracks in the lower right corner of the wall appear to form a "36" and a "75."  The intersection of 36 degrees north and 75 degrees west is in the Atlantic, just off the eastern coast of North America. 

  The nearest dry land, just a few miles to the west of those coordinates, is at Kill Devil Hills on the Outer Banks (a string of barrier islands off the North Carolina coast).

1) Pass two friends of octave

  Frank and Wilbur Wright are generally credited as being the inventors of the modern airplane and they were friends with Octave Chanute. Our landfall at Kill Devil Hills puts us at the spot where the first heavier-than-air powered flight took place: the Wright Brothers National Memorial (coordinates 36.0°N and 75.7°W).

2) In December

  The road that runs outside the Wright brothers memorial is Highway 12.  If we are to "pass" the memorial "in December," we are meant to take the highway either north or south.  (The horse-like faceplate on the suit of armor may be intended as a hint toward the town of Nags Head, which one would pass through on Hwy. 12 heading south.)

3) Ride the man of oz

  "Man of oz" would refer to L. Frank Baum, who wrote The Wizard of Oz.  Many searchers have mistakenly interpreted this line as a reference to the Thomas Baum Ferry that runs between Hatteras and Ocracoke Islands, but that ferry was only built in 1995.

  The correct reference is to the Washington Baum Bridge that connects the Outer Banks to the east side of Roanoke Island.  The bridge that is currently in place was only built in 1994, but an earlier bridge in the same place (and with the same name) was built and dedicated in 1962.  A highway sign (shown at left) makes the name clear to anyone driving over the bridge.

4) To the land near the window

  "The land near the window" refers to the outline of Roanoke Island that appears near the window in Image 3.  (Yes, it's an abstract representation, just like every other visual clue in The Secret.)

  Together, Lines 3 & 4 are telling us to turn off Route 12 and take the Washington Baum Bridge to Roanoke Island.

5) There's a road that leads to

6) Dark forest

  After crossing the Washington Baum Bridge, US Highway 64 runs through Manteo and goes to the Fort Raleigh National Historic Site at the northern tip of Roanoke Island.

  The words "dark forest" have multiple connections to the area around the historic site.  They appear on the Memorial Plaque beside the main entrance to the Elizabethan Gardens (see left). They also appear three times in the script for The Lost Colony, the long-running musical drama that is staged every summer at the Waterside Theatre.

  These lines confirm we are in the correct general area.

Our route so far:

  Now that we are at the northern tip of Roanoke Island, it's worth stopping to list the many places where a casque could not be buried:

• Most of the northern tip of the island is contained inside the Fort Raleigh National Historic Site.  The area has enormous historical significance because it's where the Roanoke Colony was established by Sir Walter Raleigh in 1587.  Archeological digs have been taking place within the historic site for decades and Preiss was clearly well aware of the land's history and importance.  There is absolutely no chance that he would have disturbed a pristine natural area where artifacts might be found.  He wouldn't be digging in any wooded or natural areas, and modern searchers shouldn't dig there either.
  
  
• The other big chunk of land at the tip of the island contains the privately-owned Elizabethan Gardens.  The guidelines for The Secret specifically rule out any possibility that a casque could be buried in "any public or private flower bed."  On top of that, it's extremely unlikely that Preiss expected us to pay admission, smuggle a shovel in our pants past a gatekeeper, and then dig in a formal garden.  Image 3 may have visual hints to some features in the gardens, but we can rule out that entire plot of land as a hiding place.
  
  
• The guidelines for The Secret also specifically say that no casques will be buried in any cemeteries, so we can rule out the small graveyard at the end of Pear Pad Road.
  
  
• The coastline of Roanoke Island is constantly reshaped by storms, and it's very unlikely that Preiss would bury a plexiglass box on a beach where shifting sands could quickly leave it uncovered.  Any spot that's directly exposed to high waves from the ocean is not a realistic possibility.  (Plus, we know from other solutions that there should always be a distinctive man-made object very near the casque, and there are no such features on the beach.)
  
  
• And (obviously) the casque could not be in a building or underneath a paved road or parking lot.

  Combining all of those restrictions eliminates more than 95% of the northern tip of Roanoke Island and narrows our search considerably.  We are now looking for a relatively sheltered place where we can dig beside some distinctive, man-made object without damaging any flowerbed, grave site, or archeologically-important area.  Onwards...

7) Where white is in color

8) With two maps

  John White (c. 1540 – c. 1593) was an English artist and colonist who was the governor of the colony on Roanoke Island.  He is now immortalized as a character in The Lost Colony, which was written by the Pulitzer Prize-winning playwright Paul Green.  So "white is in color" could refer to the watercolors painted by John White or it could refer to White being a character in a play by Green. 

  Up until very recently, a sign across from the ticket booth at the entrance to the Waterside Theatre showed two maps.  One was a historic watercolor map by John White and the other was a modern map of the Fort Raleigh National Historic Site.  An adjacent sign described the play and mentioned that the play was created by Paul Green.  So the spot by the ticket office would have worked for either interpretation of "where white is in color."

9) After circle and square

  "Circle and square" refers to the traffic circle and parking lot that one would drive through to reach the ticket booth for the Waterside Theatre. Note that the modern map shown in the upper right corner of the ticket booth sign makes these shapes very clear.  (The map also gives a clear outline to the shape of Pear Pad Road, which is also represented in Image 3.)

10) In July and August

  We know that Byron Preiss liked to make fanciful historical connections, and this line may be one of them.  "July and August" is a quotation from the top line of the Virginia Dare Memorial, which begins "On this site, in July-August, 1585."  The memorial is on the grounds of the Fort Raleigh National Historic Site and one would pass it on the way from the Visitor Center to the Waterside Theatre.

  "July and August" are also two summer months when The Lost Colony is performed.  Visitors in the modern world coming to see the performances would pass through the circle and square and see the sign with the two maps.

11) A path beckons

12) To mica and driftwood

  The mention of mica is probably just a general hint to steer searchers to the correct state.  According to one blog, "North Carolina is the nation’s leading producer of mica."

  The mention of driftwood tells us that after circle, square, and two maps we should follow a path that leads in the direction of the beach and Roanoke Sound.

  Here are those same steps shown in the order in which they would occur.  The underlying map is from a 1982 NPS planning document and should show things exactly as they would have been when Preiss was there.

1 - The "road that leads to dark forest" (the entrance road from US Highway 64).

2 - "Circle" (the traffic circle beside the Visitors Center).

3 - "Square" (the parking lot for the theater).

4 - The ticket booth where white is (or was) in color with two maps.  Tickets for performances of The Lost Colony are sold here in July and August.

5 -The trail to the Waterside Theatre.  It leads in the direction of Roanoke Sound and the beach (where there would be driftwood).  It was the only trail from the ticket booth.

6 - The Waterside Theatre.

  The Waterside Theatre is a V-shaped outdoor auditorium on the northern tip of Roanoke Island.  It has two banks of seats with a curving aisle running between them.  Just behind the stage, the shoreline spreads out on either side.

  Image 3 is showing us all those same features in a set of cracks that are centrally located on the wall. There is the V-shaped auditorium, divided by the aisle, and the shoreline spreading out to either side behind the tip of the V.

  The Waterside Theatre was originally built in 1936 by an Englishman named Albert Bell, who was known as "Skipper."  When a fire broke out and burned most of the theatre in 1947, Bell quickly rebuilt it.  And after Hurricane Donna destroyed most of the theatre in 1960, Bell was in charge of rebuilding it yet again.

  The history of the Waterside Theatre is so closely tied to this one individual that it is commonly known as "The House that Skipper Bell Built."  The placement of bells beside the outline of Roanoke Island in Image 3 strongly makes the connection and could lead searchers directly to the Waterside Theatre even without all the other clues prior to this point.

  After Bell's death in 1964, a plaque was installed in his memory at Waterside Theatre.  The plaque has a prominent place where one enters the theatre and it is the first thing one would see at the end of the path from the ticket booth. 

  Even a visitor unfamiliar with the history of the theatre could see the name "Bell" at this spot and make the connection.

  Anyone who has ever seen a performance of The Lost Colony would likely get a sense of recognition on seeing the cracks of the floor in the lower left corner of the image.  The stage at the Waterside Theatre has always featured a five-sided house structure in the middle of the back wall.  The highest point of the structure forms the tip of the peaked roof.  The two lowest points meet the floor of the stage.  And the two remaining points of the pentagon are where horizontal roofs of sheds or other structures extend out to each side.

  The cracks in the floor capture that same basic structure, with the pentagonal shape of the house meeting the horizontal lines of the stage and the sheds.  But the illustration only shows us the western half of the symmetrical structure.  We are seeing "stage right" (or "house left" from the audience's point of view).  The bell extending down to the diagram seems to be pointing, drawing our attention to that part of the stage.

  The side of the stage shown in the cracks plays a significant part in the performances of The Lost Colony.  At the end of the play, as the colonists go away, the actors troop off that end of the stage and go up a short ramp to a landing on the side before exiting.

  Let us pause now and take another look at the central figure of Image 3.  We have a central suit of armor with arms outstretched (and propped up).  The suit of armor is a metal structure and the outstretched arms are hollow metal cylinders.  They are essentially pipes.  And each arm is being used to hang various objects.

  Looking around the theatre, we can see a structure that is, in a somewhat abstract or metaphorical way, similar to the Image 3 suit of armor.  On the western edge of the auditorium there is an upright metal tower with outstretched pipes.  The pipes are fastened in place and are used to rig lights and other equipment for performances.  They are essentially outstretched metal arms used for hanging things.

13) Under that

14) Which may be last touched

15) Or first seen standing

  "Last touched or first seen" is almost certainly a reference to a tall tree.  When the colonists sailed to Roanoke Island in July of 1587, the first indication of land they would have seen over the horizon would have been the top of a tree.  When those colonists disappeared some time later, the last thing they did (apparently) was to peel the bark off the trunks of two trees and carve the letters "CROATOAN" into the trunk of one and "CRO" into the trunk of the other.  This was likely to give searchers some idea of where they went.

  The CRO tree has enormous symbolic and emotional importance, both in the play The Lost Colony and in the history of Roanoke Island.

  For performances of The Lost Colony, the crew builds a new "CRO tree" every year.  It is always on the western edge of the auditorium on a small landing, so the cast can assemble there and touch it before they parade out.

  This picture shows how the CRO tree looked in 2011.  Photo by Sarah Stierch (CC BY 4.0).

  So where does the crew build the CRO tree for The Lost Colony?  You guessed it!

  The structure around which they build the CRO tree every year is... the same metal tower with outstretched arms.  This picture shows how the tower and tree look in early summer of 2017.

16) Look north at the wing

17) And dig

18) To achieve

19) By dauntless and inconquerable

20) Determination

21) Your goal.

  The instructions that we should "look north ... and dig" strongly suggest that from the actual dig site one should be able to look northwards across the water and see the Wright Brothers National Memorial at Kill Devil Hills.  The memorial feature a large wing-shaped monument that is visible from a long ways across the water.  And the dedication at the base of that wing bears the phrase "In commemoration of the conquest of the air by the brothers Wilbur and Orville Wright conceived by genius achieved by dauntless resolution and unconquerable faith."

  Beneath the suit of armor in Image 3 there is a pedestal with cracks.  Most of the cracks are hazy and indistinct, but there's one section that is sharper and clearer than that rest.  That section seems to show a forking path with a small square in the fork.

  Aerial views show a similar set of paths at the northwest corner of the Waterside Theatre.  There is a path from the stage with a broad area beside it and then a small square where the path and wider area meet.  And that small square is the landing where the CRO tree and tower are located. 

  And that's where the casque was buried.  It is (or was) under the CRO tree, the representation of "that which may be last touched" by the unfortunate colonists of the Lost Colony.

Final Location: 35°56'22.0"N 75°42'33.4"W

(Latitude: 35.939442, Longitude: -75.709287)