瑜伽論記 7.413

7.413

一、取假名綵畫木石泥等所作骨鎖相者，三藏云：欲作不淨觀，先觀假骨。泰云：修觀行者欲不淨觀無異骨可得時，以木石等假作骨鎖方修不淨觀，既非實骨故但名鎖，若得實骨觀不淨方名骨鎖觀，由此道理辨十想云：若骨若鎖。

Regarding 'first, grasping the sign of an interconnected skeleton made nominally of colored paint, wood, stone, clay, and the like', the Tripiṭaka Master says: Wishing to practice the contemplation of impurity, one first contemplates an artificial skeleton. Tai says: When the practitioner wishing to contemplate impurity cannot obtain real bones, they artificially make an interconnected skeleton out of wood, stone, and the like, and only then cultivate the contemplation of impurity; since they are not real bones, it is merely called 'interconnected' (chain); if real bones are obtained to contemplate impurity, only then is it called the 'interconnected skeleton contemplation'. By this principle, distinguishing the ten perceptions, it says: 'either bones or a chain'.