Duchamp striptease quondam Piranesi, even
In Francis M. Naumann's "Marcel and Maria", a fascinating article on Duchamp's Ètant Donnès in Art in America, April 2001, Duchamp is quoted as having said the following:
"I want to grasp things with the mind the way the penis is grasped by the vagina."
Naumann's article is all about finding clues about meaning purposely hidden by Duchamp within his oeuvre.
Piranesi's Ichnographia Campus Martius contains a nimiety of purposely hidden clues as well.