The Mishnah tells us that a Shevu'ah that one saw a snake "like the beam used to press olives", is a Shevu'as Shav, because it can't possibly be true. The Gemara discusses what aspect of the beam cannot be found in a snake. According to the Yerushalmi, a snake can never be "square" as a beam -- because no natural objects are square. The Bavli says no snake is "Taraf" like a beam, and according to Tosfos and Rosh, the Bavli means the same as the Yerushalmi; "Taraf" means flat on four sides.

Many philosophical insights have been written based on this Yerushalmi.

Be well

M. Kornfeld