Why did he make the Yam?
Rashi: It was for Kohanim to immerse in it, like it says in Divrei ha'Yamim II, 4:6.
What is "Mutzak"?
Rashi (16): It is melted [into a mold]. Radak - the mold was in the ground. Afterwards, he beat it with a hammer.
What is "from edge to edge"?
Rashi: It is in the middle (from one edge to the opposite edge). The width of a circle is in its middle.
What is "v'Kav"?
Rashi (citing Eruvin 14b): It is the circumference; it is three times the diameter.
What is "Komaso"?
Rashi: It is its depth.
Rashi (citing Eruvin 14b) writes that the circumference is three times the diameter. This is not precise!
Tosfos ha'Rosh (14b): The verse is a source that we may rely on this approximation, which is not exact. 1
The exact ratio of the circumference to the diameter is ? (Pi) - 3:1415926
Sha'ar ha'Tziyun 372:18: Perhaps there is a tradition from Sinai to rely on this, and that a square's diagonal is seven fifths of its side, for it is tedious to be precise.
QUESTIONS ON RASHI
Rashi writes that the Yam was for Kohanim to immerse in it. Tevilah in Kelim is invalid!
Radak (26, citing Yerushalmi Yuma 3:8): The spring from Ein Eitam entered it, and there was an opening the size of a pomegranate between the oxen's feet (so it was connected to the spring).
