Keilim, Chapter 17, Mishnah 15. Much of this masechet has been occupied with measurements: how large a hole must be before a utensil stops being a utensil, how much a vessel must hold before it counts. Our mishnah turns to the opposite side of the question. Once a person deliberately fashions something to serve as a container or as a place to lie or sit, how small may it be and still be susceptible to tumah? And a second question follows: whose making counts? The mishnah closes with a striking ruling about children, and about the difference between doing something and merely thinking it.
A container of any size at all
The mishnah opens: "Ha'oseh keli kibul mikol makom, tameh." One who forms a receptacle, in whatever measure it may be, has made a keli that can contract tumah. There is no minimum volume here. Even a receptacle that holds the tiniest quantity is a real vessel, because a person set out to make it a container and it functions as one.
This rule governs vessels of wood and of leather, and other materials of that kind. Earthenware, however, is the exception: as we learned earlier in the masechet, a keli cheres does have a minimum capacity before it becomes susceptible to tumah.
A bed or seat of any size
The next clause of the mishnah shifts from receptacles to surfaces meant for the body: "ha'oseh mishkav umoshav," one who prepares an item on which a person will lie down or sit. And of such an item the mishnah says "mikol makom," no matter what its dimensions may be, that it is "tameh." No lower limit is imposed here either. Tumat midras is the tumah at issue: when a zav, or anyone or anything carrying that grade of tumah, presses his weight down upon an article that was produced precisely for being lain or sat upon, the article contracts that tumah. Because this object was set aside for supporting a person at rest, its small dimensions are irrelevant, and midras takes hold.
A pouch of raw hide or of paper
The mishnah proceeds to the substances from which a receptacle may be built: "ha'oseh kis," one who constructs a pouch, whether "me'or hamatzah," from hide that never went through the tanning process and remained raw, or "min haneyar," from paper. Such a pouch, the mishnah rules, is "tameh." One could easily have assumed that only properly finished leather has the standing of vessel material. The mishnah rejects that assumption: untanned skin, and even a sheet of paper, are adequate stuff out of which a true keli is formed, and the pouch is therefore open to tumah.
Shells hollowed out by children
The mishnah now turns to items produced by youngsters at their games: "harimon, ha'alon veha'egoz" refers to the rind of a pomegranate, the cup of an acorn and the shell of a walnut, and about them the mishnah says "shechakakum hatinokot," that youngsters scooped them out and made a cavity in them. For what purpose? "Lamod bahem et he'afar," to use them for measuring out earth, or alternatively "shehitkinum lechaf moznayim," meaning they shaped the shell to function as the dish of a toy balance. The verdict of the mishnah in each of these cases is "tameh": the hollowed shell has the halachic standing of a keli and is open to tumah.
Why does a child's plaything qualify as a vessel? Because the shells of these fruits and nuts are sturdy and hold up over time. That is the operative principle: a receptacle whose material will endure counts as a keli, while a receptacle made of something that lasts only a short while does not. Anything that will not survive is not treated as a vessel at all. A pomegranate rind, an acorn cup and a walnut shell, however, last long enough to be genuine utensils.
Their action counts, their intention does not
The mishnah supplies the reasoning for this ruling in a compact formulation. "Sheyesh lahem ma'aseh," a minor is credited with what he does with his hands, "ve'ein lahem machshavah," but he is not credited with what he resolves in his mind. The deed of a child is halachically effective; his designation by thought alone is not.
Consider what this means in practice. If a minor comes across a shell and decides in his mind that he will use it as a container, nothing happens. His thought accomplishes nothing, and the shell does not become a keli. An adult in the identical situation is treated altogether differently: were an adult to decide to use that shell as a receptacle, the decision alone would be sufficient to make it a vessel, even without lifting a finger to alter it. For a child, thought is halachically empty.
His hands, though, are another matter. A child's deed does have standing. When he takes the pomegranate, the acorn or the walnut and actually works on it, scraping and hollowing it out so that it will hold dirt or serve as the pan of his little scale, that act itself transforms the shell into a keli. And once it is a keli, it is subject to tumah like any other vessel.
So this mishnah leaves us with two clear lessons. First, when a person intentionally makes a container, or a surface to lie or sit upon, size is no obstacle: any capacity at all suffices (with earthenware the one exception), and even raw hide or paper serves as vessel material. Second, the making itself must be real. Durable materials produce vessels while perishable ones do not, and a minor's hands can create a keli even though his mind cannot.