Blood-letting measuring device

Blood-letting device as described by Ismail ibn al-Razzaz al-Jazari in his "Book of Knowledge and Ingenious Mechanical Devices", AD 1204-6, reconstructed 1977.

The book described the construction, components, and functions of 50 mechanical devices, or automata. This device measured the blood lost during phlebotomy (blood-letting) sessions, a popular therapy in the Arab world. Two scribes are seated above the device and their actions describe the amount of blood to be let.