Illustrated Companion to the Latin Dictionary/Tribulus

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. 

TRIB'ULUS (τρίβολος). A caltrop; that is, a contrivance consisting of four strong iron spikes projecting from the sides of a ball of the same metal, and arranged in such a manner, that when thrown upon the ground, one of them would always stand upright, as in the annexed example (Tribulus/1.1), from an original. It was employed in ancient warfare for the purpose of impeding a charge of cavalry, being thrown on the ground to wound the horses' feet. Veg. Mil. iii. 24.

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  Tribulus/1.1