Marcel Duchamp, Rotary Glass Plates (Precision Optics), 1920
If you are curious to see this artwork in motion, watch a video on vimeo.
"Five painted plastic plates turning on a metal axis and forming continuous circles when seen in motion from a distance of one meter. I made this version for a sculpture class, taught by artist Stephan von Huene, in response to a design problem dealing with spatial concepts. Chouinard Art Institue, Los Angeles, CA. 1969."