四分律刪繁補闕行事鈔 1.146

1.146

Undergoing parivāsa: formerly it was said to mean not completely assembling within the same boundary; now it refers to mistakenly including bhikṣus outside the boundary in the count. It does not mean seeing them with one's eyes outside the boundary; because the boundary limits are not known, and they are unseen outside, the performance of the act is invalidated, and thus it is said that they do not make up the quorum.