Gui Jian (鬼箭)

Gui Jian, from 'Ji Xiao Xin Shu (《紀效新書》)'.

Gui Jian (鬼箭, lit. 'Ghost arrow') was a type of iron caltrop that was cooked with either human feces or poison so that it wouldcause infection when stepped on. It was a very dirty weapon and poses great danger to its user, and thus usually stored inside a container made of bamboo. Instead of planting the caltrops one by one, user of Gui Jian simply scattered the caltrops directly from the container.