This is a ready-made dating back from 1916. It is a ball of twine between two plaques of copper, brass. Before I finished it Arensberg put something inside of the ball of twine, and never told me what it was, and I didn’t want to know. It was a sort of secret between us, and it makes a noise, so we called this a ready-made with a hidden noise. Listen to it. I don’t know; I will never know whether it is a diamond or a coin.

— Marcel Duchamp, “A Conversation with Marcel Duchamp,” television interview conducted by James Johnson Sweeney, NBC, January 1956 (filmed at the Philadelphia Museum of Art), via THE WRITINGS OF MARCEL DUCHAMP