showstudio:

Man Ray, “Indestructible Object (or Object to Be Destroyed)”, originally 1923.

Instructions are found on the back: “Cut out the eye from the photograph of one who has been loved but is seen no more. Attach the eye to the pendulum of a metronome and regulate the weight to suit the tempo desired. Keep going to the limit of endurance. With a hammer well-aimed, try to destroy the whole at a single blow.”