Hourglass, reign of Ptolemy II Philadelphus, 285/82-246 B.C.
Rome, Museo Barracco, inv. 27

Water clocks were used to measure intervals of time at night, probably in a temple environment: the water drained out of a hole in the base and the hour could be read on the monthly hour scales marked by notches on the inside wall. The god who was honoured as the patron of the month was portrayed on the outside. In the surviving frames we can recognise the first two gods of the year (Tekhyt and Ptah) and the last four (Khonsu, Horus-Khentykhety, Ipet-hemetes and Ra-Harakhty).