Slave Market with the Disappearing Bust of Voltaire
(1940)
Oil on canvas
18 1/4 x 25 3/4 inches

This is a perfect example of an instantaneous paranoiac critical transformation. Dali had long been experimenting with the idea of double imagery, and this work so perfectly exemplifies it that it was used by the cover of Scientific American in 1971 to illustrate the concept.