Simultaneously clear, yet undeniably impenetrable, there is a haunting poetry in Alfred Jensen's work. The Reciprocal Relation of Unity: 20-40-60-80, seems simple-flat, thickly painted checkerboards of brightly quilted color, numbered and bordered with obscure mathematical symbols and equations-a combination of colors, patterns and geometries that are somehow classically familiar. Yet, here, Jensen explores a dated and rigorous mathematical equation. Demonstrating the use of reciprocal relations, the equations from which Jensen draws his title, 1 x 20, 2 x 20, 3 x20, 4 x 20, form the beginning of the vigesimal system (20-40-60-80), which was in use during the archaic period of the Chinese, Egyptian, Green and Mayan cultures. "I find in the square specific settings, divisible areas, number structures, possibilities of time measure and rhythm as well as the essential form of color," Jensen explains. "The square's capacity latent in its arithmetical mean brings forth a reciprocal relation between the outwardly increasing area, and the inwardly decreasing area of the square. This coordination of number structures enabled the archaic people to erect temples and pyramids" (A. Jensen, quoted in W. Schmied, Alfred Jensen, exh. cat. Kestner-Gesellschaft, Hannover, 1973, p. 39). The colorful and highly decorative surface of Jensen's work, though directly evocative of game boards, Persian rugs, tiled floors, Tantric diagrams, and illuminated manuscripts, are in fact-through their complex systems of numbers-recollections of Jensen's trip to the Yucatan, coupled with his readings on Mayan culture.