Al-Jazari's Scribe Clock

In another of his clock designs, 12th century engineer Al-Jazari adapted a water clepsydra—a water vessel with a hole for water to escape—to make a Scribe Clock.

He included the design in his manuscript 'The Book of Knowledge of Ingenious Mechanical Devices'.

Controlled by the water moving steadily downward, the float moves down pulling a string which rotates a pulley. The scribe sitting on top of this clock would turn steadily to point at the time with his pen.