π: A Line of Thirty Cubits Going all Around
“Whatsoever has a circumference of three handbreadths is one handbreadth in diameter (Mishnah). Is it so?—Rabbi Yoḥanan replied: Scripture stated: And he made the cast metal sea ten cubits from edge to edge, circular all around, and five cubits in height and a line of thirty cubits going all around (1 Kings 7:23). But surely there was its brim?—Rav Papa replied: Of its brim, it is written in Scripture: [a mere] blossom of a lily; as is written: its thickness was a handspan, and its rim like the design of a cup’s rim, blossom and lily, two thousand bats did it hold (ibid., 26) [the bat is a relatively large unit of liquid measure, but the precise quantity is uncertain]. But there was [still] a fraction at least?—when it was reckoned it was that of the inner circumference [this is the only instance where a doubt is raised in the Talmud in connection with a mathematical statement, proving that the rabbis were well aware of the more exact ratio between the diameter and circumference and that the ratio of 1:3 was accepted by them simply as a workable number for religious purposes, cf. BT Eruvin 76a; Sukkah 7b]” (BT Eruvin 14a).
“Rabbi Abba opened, saying, ‘He made the sea [cast metal] (1 Kings 7:23), and it is written: Standing upon twelve oxen: three facing north, three facing west, three facing south, and three facing east, with the sea set upon them above… (ibid., 25), and it is written: the twelve oxen underneath the sea (ibid., 44). Standing upon twelve oxen—certainly so! For this sea [Shekhinah] is arrayed by twelve in two worlds: by twelve above, appointed by chariots; by twelve below, twelve tribes” (Zohar 1:241a).