‘Body Pressure’, a 1974 performance piece by Bruce Nauman.

The performer is instructed (through a poster hung on the wall) to press himself against the wall in various positions. The poster is also a free edition.

The text from this poster is below.

Body Pressure
Press as much of the front surface of
your body (palms in or out, left or right cheek)
against the wall as possible.
Press very hard and concentrate.
Form an image of yourself (suppose you
had just stepped forward) on the
opposite side of the wall pressing
back against the wall very hard.
Press very hard and concentrate on the image pressing very hard.
(the image of pressing very hard)
press your front surface and back surface
toward each other and begin to ignore or
block the thickness of the wall. (remove
the wall)
Think how various parts of your body
press against the wall; which parts
touch and which do not.
Consider the parts of your back which
press against the wall; press hard and
feel how the front and back of your
body press together.
Concentrate on the tension in the muscles,
pain where bones meet, fleshy deformations that occur under pressure; consider
body hair, perspiration, odors (smells).
This may become a very erotic exercise.