Jaeger-LeCoultre Atmos Clock

Jaeger-LeCoultre Atmos clocks, perfected in 1928, consist of mechanisms that are capable of transforming ambient variations in temperature and atmosphere into mechanical energy. In every Atmos clock, there is a capsule that is filled with ethylene chloride gas and, as temperature/atmosphere rises/falls, this gas is able to expand/contract accordingly which in-turn expands/contracts the capsule (bellows). As the bellows are connected to a short chain, this reciprcating motion will wind the mainspring.

This is the closest item we currently have to perpetual motion.