The 18th-century pocket watch

'There was no device for keeping accurate time at sea until John Harrison, a carpenter and instrument maker, refined techniques for temperature compensation and found new ways of reducing friction. By 1761, he had built a marine chronometer with a spring and balance wheel escapement that kept very accurate time. With the final version of his chronometer, which looked like a large pocket watch, he achieved a means of determining longitude to within one-half a degree.'

(https://nrich.maths.org/6070)