I like to work from things that I see, whether they're man-made or natural or a combination of the two... The things that I'm interested in have always been there. The idea of a shadow and a natural object has existed, like the shadow of the pyramids, or a rock and its shadow; I'm not interested in the texture of the rock, or that it is a rock, but in the mass of it, and its shadows.

Quote in an interview by Henry Geldzahler, 'Art International 1.', February 1964, p. 48