Muhammad ibn Abī Bakr al Ibarī (13th century)
Astrolabe with geared calendar, 1221-1222
Oxford, Museum of the History of Science, inv. 48213
This Persian astrolabe is the oldest complete device with cog wheels to have come down to us. On the front side it is an astrolabe, linked to the calendar by a gear train. On the back, the disc shows the phases of the Moon.