Siege Crossbow (Civ3)/Civilopedia

The siege crossbow predates the smaller hand crossbow by hundreds of
years, in both China and Europe. Roman armies often used crossbow-like
weapons called ballistae to assault light fortifications and damage
heavy enemy formations. In Asia, siege crossbows were used to throw
stones along a straight trajectory with great force -- the draw weight
of a siege crossbow could go as high as 2,000 pounds. The siege
crossbows used in Japan were probably adapted from Chinese designs,
which were used as early as 500 B.C.E.