If it (the korah) were of straw or of reeds, it is viewed as if it were made of metal. [R. Yehudah says this. The halachah is not in accordance with him.] If it were crooked, [so that an ariach could not rest upon it (as it also could not if it were round)], it is viewed as if it were straight. If it were round, it is viewed as if it were square. Whatever is three tefachim in circumference is one tefach in width. [That is, what is the required measure for a round korah? Whatever is three tefachim in circumference — i.e., whatever requires a cord three tefachim long to go around it — would, if squared, have a width of a tefach. For thus do we find with the yam (the reservoir) made by Solomon, viz. (I Kings 7:23): "And he made the molten yam, ten cubits from brim to brim, round all about … and a line of thirty cubits compassed it roundabout" — whence it is seen that for every cubit of width in the circle, there are three cubits of circumference.]
Bartenura on Mishnah Eruvin
היתה של קש ושל קנים – Rabbi Yehuda stated this but the Halakha is not according to him.
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English Explanation of Mishnah Eruvin
Introduction
This mishnah is a continuation of Rabbi Judah’s words from yesterday’s mishnah. Rabbi Judah held that the cross-beam need not actually be strong enough to support a half-brick.
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Bartenura on Mishnah Eruvin
עקומה – the small bricks are not able to rest upon it (when it is curved) and similarly when it is round, a small brick cannot rest upon it.
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English Explanation of Mishnah Eruvin
If [the cross-beam] was made of straw or reeds, we look at it as if it was of metal. If the cross-beam was made of a material which could not hold a half-brick, Rabbi Judah considers it nevertheless as if it was strong enough to do so.
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Bartenura on Mishnah Eruvin
if it has in its circumference: Which is to say, what is the round measurement required to render [the beam] proper? Anything that has in its circumference three handbreadths, which requires a string of three handbreadths to encircle it around, it is known that it has a width (diameter) of one handbreadth, if you divide [it]. As so do we find with the basin that Shlomo made (II Chronicles 4:2), "ten ells from its edge to its edge and five ells of height and a line of thirty ells encircling it around." Hence for every ell in width (diameter), there are three ells in circumference.
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English Explanation of Mishnah Eruvin
[If it was] curved we look at it as if it were straight. If it was curved, it also could not hold a half-brick. Nevertheless, Rabbi Judah holds that it is valid.
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English Explanation of Mishnah Eruvin
[If it was] round we look at it as if it were square. Whatever has a circumference of three handbreadths has a diameter of one handbreadth. Again, a round cross-beam could not hold a half-brick. However, it still must be wide enough to hold a one handbreadth half-brick. In order for this to be true, it must have a circumference of three handbreadths (the rabbis knew that pi was roughly three to one, and they knew that this was not exact).
