Early Egyptian water clock, 1415-1380 BC.
© Science Museum / Science & Society Picture Library
The original of this plaster cast (which is held in the Cairo Museum) was found at Karnak Temple, Upper Egypt, in 1904, and dates from the reign of King Amenhotep III (1415-1380 BC). It is made of alabaster and was probably used for indicating the pasage of hours of the night. In use, the vesel was filled with water, which leaked out slowly from a small hole near the bottom; the time being indicated by the level of the water remaining within.