In 807 the Abbasid caliph in Baghdad, Harun al-Rashid, sent Charlemagne a gift the like of which had never been seen in the Christian empire: a brass water clock. It chimed the hours by dropping small metal balls into a bowl. Instead of a numbered dial, the clock displayed the time with 12 mechanical horsemen that popped out of small windows, rather like an Advent calendar.
It was a thing of beauty and ingenuity, and the Frankish chronicler who recorded the gift marvelled how it had been ‘wondrously wrought by mechanical art’. But given the earliness of the date, what’s not clear is quite what he might have meant by that.
Certain technologies are so characteristic of their historical milieux that they serve as a kind of shorthand.