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.
 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.