Ballista

The ballista, plural ballistae, sometimes called a bolt thrower, was an ancient projectile weapon that launched either bolts or stones at a distant target. Developed from earlier Greek weapons, it worked by using two levers with torsion springs, made of twisted skeins of cord, rather than the tension bow of a crossbow. Early ballistae projected heavy darts or stone projectiles for siege warfare, and the design later developed into a smaller precision weapon called the scorpio.