瑜伽論記 6.512

6.512

朽穢不淨有二：一者、依內即觀自身三十六種不淨之物；二者、依外則觀他身十六種不淨之事。

Decayed and vile impurity has two aspects: first, based on the internal, which is observing the thirty-six kinds of impure substances of one's own body; second, based on the external, which is observing the sixteen kinds of impure matters of another's body.