R. Hiyya taught: A fish-pond between two Sabbath limits requires an iron wall to divide it [into two independent sections].
R. Jose son of R. Hanina laughed at him.
The pond stands at the limit of two different Shabbat zones - with the "boundary" between them in the middle of the water. If residents of either zone wish to take water or fish from the pond they would have to take it from their half only. R. Hiyya wants an iron wall to split the pond so that the water cannot co-mingle.
Why does R. Jose find this so funny? Is it because he believes a wall of reeds would suffice? Or because the water could never really be divided?
Or is it just funny?
More rabbi humor:
R. Mesharsheya requested his son: When you visit R. Papa, ask him whether the four cubits of which the Rabbis have spoken are measured by the arm of each individual concerned or by the standard cubit used for sacred objects.There is a four cubit limit of movement in some instances on Shabbat. But there are two different "cubit" measurements used: the forearm of the individual (which varies) or the "sacred objects" one, based on the measurement of Moses' forearm. This matters because four cubits is just a little more than a human lying down. So which is it?
If he tells you that the measurement is to be made by the cubit used for sacred objects, [ask him:] What should be done in the case of (the giant) Og the king of Bashan; and if he tells you that the measurement is to be made by the arm of each individual concerned, ask him: Why was not this measurement taught among those which the Rabbis have prescribed in accordance with each individual?’
When he came to R. Papa the latter told him: ‘If we had been so punctilious we would not have learnt anything!Ha!
The fact is that the measurement is calculated by the arm of each individual concerned, and as to your objection, "Why was not this measurement taught among those which the Rabbis have prescribed in accordance with each individual", [it may be explained] that the ruling could not be regarded as definite since [even a normal person] may have stumped limbs’Ok, that's not funny. But it does show that there is a need for a more standard measurement.