Mishnà su Esodo 30:40

Hillel says: “A hin full of drawn water renders the mikweh unfit.” (However, man must speak in the language of his teacher.) And Shammai says: “Nine kavs.” But the Sages say: “Neither according to the opinion of this one nor according to the opinion of this one;” But when two weavers from the dung-gate which is in Jerusalem came and testified in the name of Shemaiah and Avtalion, “Three logs of drawn water render the mikweh unfit,” the Sages confirmed their statement.

The laver was between the porch and the altar, a little to the south. Between the porch and the altar there were twenty-two cubits. There were twelve steps there, each step being half a cubit high and a cubit broad. There was a cubit, a cubit and a level space of three cubits, then a cubit, a cubit and a level space of three cubits, then at the top a cubit, a cubit and a level space of four cubits. Rabbi Judah says that at the top there was a cubit, a cubit and a level space of five cubits.