首楞嚴義疏注經 6.223

6.223

周利槃特因作數息，微細窮盡生住異滅，返息循空，因是得道。今云鼻息雖通出入，出入各據而不相交，支分既離，豈成圓觀。

Cūḍapanthaka, by counting breaths, exhaustively investigated arising, abiding, changing, and ceasing in subtle detail, turning breath back to follow emptiness, and from this attained the Path. Here it is said: although the nasal breath passes in and out, outgoing and incoming each occupy their own position without mingling; since their branches are separated, how could it constitute perfect contemplation?