In the second passage from Rev. Kenner Davenport’s The Reasonable Horologist, he reflects on man’s early attempts to capture time more precisely. Clepsydra refers to a water clock (its Greek translation is “water thief”) which measures time by regulating the flow of liquid from one vessel to another.
In 807, Emperor Charlemagne was sent a brass clock by the Abbasid caliph, Harun al-Rashid in Baghdad. According to the Emperor’s biographer, it was a “marvellous mechanical contraption, in which the course of the twelve hours moved according to a water clock, with as many brazen little balls, which fell down on the hour and through their fall made a cymbal ring underneath. On this clock there were also twelve horsemen who at the end of each hour stepped out of twelve windows, closing the previously open windows by their movements.” HistoryToday “Charlemagne’s Elephant”, Richard Hodges, November 2000.