ballista
ballista [Ar].A large military catapult which fired projectiles of iron or stone. Roman examples were made up of a framework in which twisted tendons, rope or leather thongs provided elasticity and force. When the twist was suddenly released, a stone of up to 45kg in weight could be thrown a considerable distance to batter a wall. The most famous ballista bolt in Britain is that piercing the spine of a man buried at Maiden Castle. Ballistaria or ballista platforms can still be detected in some forts. In the later Roman period ballistae were mounted on bastions projecting from fort walls.