Illustrated Companion to the Latin Dictionary/Onager

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

ON'AGER. A powerful engine employed in sieges for discharging missiles and stones of great weight. It is described at length by Ammianus (xxiii. 4.); but the details of machinery are always obscure, when the actual form of the object itself is unknown.