Water clocks were among the earliest timekeepers that didn't depend on the observation of celestial bodies. Water clocks were used in ancient Babylon, Mesopotami, China, Korea, Egypt, Greece, India, Arabia, Muslim and civilizations.
One of the oldest water clocks was found in the tomb of Amenhotep I, buried around 1500 B.C.
Later they were named clepsydras ('water thief') by the Greeks, who began using them about 325 B.C. These were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom.