Originally its use was not limited to Buddhism only, but was used in all the Indian ancient religions; gyoja's penance such as fasting or sitting on a batch of needles are especially famous.
本来は仏教に限らず、広く古代インド宗教全般に見られ、特に断食行や針山の上に坐禅をするなどの苦行の行者が有名である。