Khuddakavatthukkhandhaka

Vinayapiṭaka · Cūḷavagga (2) · Vol. 7 · Section 193

[193] Now at that time the privy (vaccakuṭī) was unenclosed. The bhikkhus reported this matter to the Blessed One. "Bhikkhus, I allow it to be enclosed with three kinds of walls: a brick wall, a stone wall, and a wooden wall."

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.

This passage also appears in 1 other place

Vol. 7 · Section 93 — Khuddakavatthukkhandhaka