Late in the Western Roman Empire they developed a hand spanned crossbow called an arcuballista, that consisted of a wood or composite bow on and a short stock with a hand grip on the butt end and used a rotating nut trigger system.  The design is taken from two stone reliefs of the weapon.

See the bow shooting here:

Specification

• This bow is hand spanned
• Ash stock and slider
• Antler nut
• Modern linen covered composite bow
• Linen string
• Range – around 130m/145yds