Photograph of reconstructions of Greco-Roman throwing weapons in the Saalburg Museum in Hessen, Germany.  Left standing: Polybolos, a third century BCE repeating catapult. Right standing: Philo's Chalkotonon, a bronze-spring catapult. Bottom center: Wooden chain-drive mechanism of the Polybolos. Bottom right: Philo's aerotonon, a pneumatic catapult displayed without tripod stand.  Background, on wall: Gastraphetes, a Greek crossbow.