Wunderlich's Bistable Octahedron
This Demonstration shows Wunderlich's bistable octahedron, also known as the jumping octahedron. The polyhedron was discovered by Wunderlich in 1965 and Schoenhardt in 1928. It is formed from a triangular prism by twisting the top relative to the base. A stable condition is obtained when the top touches the cylinder constructed on the base.
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 M. Goldberg, "Unstable Polyhedral Structures," Mathematics Magazine, 51(3), 1978 pp. 165–170. www.jstor.org/stable/2689996.
 I. Izmestiev, "Examples of Infinitesimally Flexible 3-Dimensional Hyperbolic Cone-Manifolds," Journal of the Mathematical Society of Japan, 63(2), pp. 581–598. projecteuclid.org/euclid.jmsj/1303737798.