Dictionary Definition :
Definition[1]
:
The three rsis or wise men and the two devas, i.e. 迦毘羅 Kapila, founder of the Sāmkhya philosophy; 鵂鶹 or 優樓佉 Ulūka or Kanāda, founder of the 勝論宗 or Vaiśesika philosophy; and 勒沙婆 Rsabha, founder of the Nirgranthas; with Śiva and Visnu as the two deities.
Source
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A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous
Definition[2]
:
(名數)三仙者:一、迦毘羅仙,數論之祖也。二、鵂鶹仙,勝論之祖也。三、勒沙婆仙,尼犍子之祖也。二天者,一、大自在天。二、毘紐天。大部輔注一曰:「一、伽毘羅,此云黃頭,頭如金色;二、優樓僧佉,此云鵂鶹仙;三、勒沙婆,此云苦行;此即三仙也。一、摩醯首羅,此云大自在天;二、毘紐,亦云韋紐,亦云韋糅,此云遍勝,亦云遍淨,及云遍悶,;此即二天也。」
Source
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丁福保《佛學大辭典》