Goldberg's Tristable Polyhedron
This Demonstration shows Goldberg's tristable polyhedron. According to Goldberg, the given polygons allow three states. Real materials deform only by small amounts, allowing the polyhedron to appear to flex.
 P. R. Cromwell, Polyhedra, New York: Cambridge University Press, 1997, p. 224.
 M. Goldberg, "Unstable Polyhedral Structures," Mathematics Magazine, 51, 1978 pp. 165–170.
 D. Wells, The Penguin Dictionary of Curious and Interesting Geometry, London: Penguin, 1991 p. 161.