A pendulum clock in Dunedin, New Zealand, has been running for 156 years without being wound.
Arthur Beverly was an astronomer who made telescope lenses and watches, and the so-called Beverly Clock was his masterwork. The concept behind it is impressive. There’s an airtight box attached to a weight. As the outside temperature goes up or down the air in the box expands or contracts. That change over the course of a day is enough to lift up the weight a little bit, and that’s enough to keep the clock going.
A change of 3.3°C over the course of a day is enough to wind this clock. And in the University of Otago, Dunedin, where the Beverly Clock is housed, the difference between the average low temperature and the average high temperature each month is always more than 3.3°C. That’s not foolproof proof, of course: individual days could easily fall under that necessary change. And indeed the clock has stopped on occasion when the temperature difference isn’t enough… but it always starts back up again without outside intervention.
Beverly built the clock in 1864, and it has not been wound since that year. A few other clocks operate under similar principles: Cox’s timepiece is driven by a mercury barometer and was built in the 1760s, but it was switched off when it went to the Victoria and Albert Museum. You can buy an Atmos clock – which likewise runs on changes in temperature and atmospheric pressure – if you have US$6,950 handy.
[Thanks to Gareth E. for suggesting this topic.]