Keilim, Chapter 2, Mishnah 4. This chapter deals with the tumah of earthenware utensils, and our mishnah applies one governing principle to three very different objects from daily life: a vessel of earthenware is susceptible to tumah only when it has a beit kibul, a place that actually holds something. Where the item is flat, or open at both ends, it is not a receptacle at all, and it stays tahor. The mishnah tests this rule on a lantern, on a potter's wheel, and on a funnel.
The lantern
A lantern in those days was an enclosed casing into which an oil lamp was set. Its purpose was to shield the flame so that the wind would not blow it out. Nowadays we would naturally think of glass, something like a bulb, but then the casing was made of earthenware, and holes were pierced in it so that the light could shine through.
Our mishnah rules concerning a "panas", a lantern: if it contains a "beit kibul shemen", a hollow that holds the oil, it is "tameh", and if it has none, it is "tahor". Picture the first type: the clay lantern is itself shaped with a sunken basin ringed by a lip. The user need do nothing more than fill that basin with oil, lay in a wick and kindle it. Since the oil sits within the utensil's own hollow, the lantern qualifies as a container and can contract tumah. The second type has no such hollow at all. Its surface is level, offering a place where a separate lamp may be set down, but there is nothing in it to hold oil. Serving as a stand does not turn an object into a container, so this lantern remains tahor.
The potter's wheel
The next item is the wheel with which the potter shapes clay into vessels. It was built of two round stones fixed to a post, the larger one below and the smaller one above. The craftsman set his foot on the lower stone to keep the wheel turning, much as we picture a spinning wheel for clay today, while with his hands he worked the clay resting on the upper stone.
Concerning this wheel the mishnah draws a distinction. "Meguphat hayotzrin", the potter's wheel, "shehu poteach bah", the one on which he begins forming the vessel, is "tehorah", because its working surface is level and encloses nothing. But "veshehu gomer bah teme'ah", the wheel used for the final stage of the job, is susceptible. Potters worked with two different wheels, and the one reserved for finishing was built with a raised border, edges running around the surface to keep the soft clay from sliding away while the craftsman brought the vessel to completion. That border turns the wheel into a true beit kibul.
The funnel
A funnel has the shape of a container, yet it cannot actually hold liquid, because there is an opening at its bottom. It is used for pouring wine or oil from one vessel into another, whether one is consolidating or simply transferring, and it prevents spillage. Nevertheless, the mishnah teaches that certain funnels do count as receptacles, even though they were not made to hold their contents permanently.
The mishnah distinguishes according to the owner. "Mashpeich shel ba'alei batim" is "tahor": an ordinary household funnel is open above and below, and nothing at all stays inside it. But "veshel rochlin tameh", the funnel belonging to a peddler is susceptible, "mipnei shehu shel midah", since he employs it as a measuring device. A peddler's funnel was built to a fixed capacity. When a customer asked for a given quantity, the peddler sealed the lower opening with his fingertip and poured in until the funnel stood full to its brim. He now knew precisely how much he was selling, and set his price on that basis. Once the terms were agreed, he lifted his finger and the wine or oil ran down into the purchaser's jug.
The mishnah then names the Tanna behind this halachah: "divrei", these are the words, of "Rebbi Yehudah ben Beterah".
The view of Rebbi Akiva
Rebbi Akiva presents his own reasoning: "mipnei shehu matehu", because the seller leans the funnel "al tzido", onto its side, "umariach bo lalo'ke'ach", giving the prospective purchaser a chance to catch the scent of what is inside. In Rebbi Akiva's opinion, then, a peddler's funnel is susceptible even where it never served for measuring at all. Funnels of this sort were formed with bellied, outward curving walls, so that once the funnel is laid over sideways a bit of the wine settles into that bulge, close enough for the shopper's nose. Since the utensil is regularly put to this use, the curve functions as a receptacle and the funnel can contract tumah, quite apart from the measuring use that Rebbi Yehudah ben Beterah described.
Rebbi Yehudah ben Beterah would not accept this. In his view, a peddler's funnel counts as a receptacle only when it is used in the ordinary way, standing upright and filled as a measure. Holding it on its side so that a little liquid collects for someone to smell is not its normal manner of use, and therefore, according to him, such an earthenware funnel remains tahor always.
So the mishnah has taken us through three utensils, a lantern, a potter's wheel and a funnel, and in each case the question was the same: does this earthenware object truly contain something? Where it does, it enters the world of tumah; where it does not, it stays tahor. And with the funnel we discovered that even a use as slight as tilting it for a customer to smell can be enough, according to Rebbi Akiva, to turn a piece of earthenware into a vessel.