Gears from the Greeks: The Antikythera Mechanism -- A Calendar Computer from ca. 80 B.C., Transactions, American Philosophical Society (vol. 64, part 7)

The first great discovery in underwater archaeology yielded not only a fine collection of art treasures but also the most enigmatic, most complicated piece of scientific machinery known from antiquity. This artifact is now identified as an astronomical or calendrical calculating device involving a very sophisticated arrangement of more than thirty gear-wheels.