Rattleback

[1] This counterintuitive behavior makes the rattleback a physical curiosity that has excited human imagination since prehistoric times.

Archeologists who investigated ancient Celtic and Egyptian sites in the 19th century found celts which exhibited the spin-reversal motion.

[citation needed] The antiquarian word celt (the "c" is soft, pronounced as "s") describes lithic tools and weapons shaped like an adze, axe, chisel, or hoe.

The first modern descriptions of these celts were published in the 1890s when Gilbert Walker wrote his "On a curious dynamical property of celts" for the Proceedings of the Cambridge Philosophical Society in Cambridge, England, and "On a dynamical top" for the Quarterly Journal of Pure and Applied Mathematics in Somerville, Massachusetts, US.

[8] The previous papers were based on simplified assumptions and limited to studying local instability of its steady-state oscillation.

Numerical simulations predict that a rattleback situated on a harmonically oscillating base can exhibit rich bifurcation dynamics, including different types of periodic, quasi-periodic and chaotic motions.