From: The World In Your Head by Steven Lehar

Fig. 5.2 (A) This figure produces a bistable percept whose spontaneous reversal is seen to simultaneously reverse the perceived direction of illumination. (B) Isolation of one pair of panels from the figure results in a tri-stable percept, whose three states correspond to (C) a convex corner illuminated from the left, (D) a concave corner illuminated from the right, or (E) two diamond-shaped tiles in the plane of the page with no percept of illumination. This phenomenon reveals the close coupling between the perception of structure and illumination, as well as perceived surface reflectance.