Ballista - siege machine

The ballista (Latin, from Greek βαλλίστρα - ballistra and that from - βάλλω ballō, "to throw"), plural ballistae, was a weapon developed from earlier Greek weapons. It relied upon different mechanics, using two levers with torsion springs instead of a prod, the springs consisting of several loops of twisted skeins. Early versions ejected heavy darts or spherical stone projectiles of various sizes for siege warfare. It developed into a smaller sniper weapon, the Scorpio, and possibly the polybolos.