Water clocks

Water clocks, all along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the cognomen and day-counting tally stick. Given their great antique, where and when they first existed is not known and perhaps unknowable. The simplest forms of water clocks, the bowl-shaped outflow type, are known to have existed in Babylon and in Egypt around the 16th century B.C. Other regions of the world, including India and China, also have early proof of water clocks but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC.