I know its been mentioned a couple times… But the Kryptos Sculpture at the CIA headquarters talks in a round about way like Qs hints.
The text is in 4 parts. 3 Have been solved and read what they say. The 4th has yet to be solved.
#1 (mispelling with Q purposeful)
Between subtle shading and the absence of light lies the nuance of iqlusion.
#2
It was totally invisible Hows that possible? They used the Earths magnetic field X
The information was gathered and transmitted undergruund to an unknown location X
Does Langley know about this? They should Its buried out there somewhere X
Who knows the exact location? Only WW This was his last message X
Thirty eight degrees fifty seven minutes six point five seconds north
Seventy seven degrees eight minutes forty four seconds west ID by rows
#3
Slowly, desparatly slowly, the remains of passage debris that encumbered the lower
Part of the doorway was removed. With trembling hands i made a tiny breach in the upper
Lefthand corner and then widening the hole a little i inserted the candle and peered
in. The hot air escaping from the chamber caused the flame to flicker but presently
Details of the room within emerged from the mist x can you see anything Q?
=
https://www.math.ucsd.edu/~crypto/Projects/KarlWang/index2.html
Notice the copper.