History of Timekeeping Devices in Egypt - Merkhets

Using plumb-lines called "merkhets", the Egyptians could calculate time at night, provided the stars were visible. Used since at least 600 BC, two of these instruments were aligned with Polaris, the North pole star, creating a north-south meridian. By observing certain stars as they crossed the line created with the merkhets, they could accurately gauge time.