Keilim, Chapter 7, Mishnah 4. This chapter deals with the tumah of the kirah, the earthenware stove, and with the various parts and attachments that surround it. One of those attachments is the chatzar hakirah, literally the "courtyard" of the stove: a ledge or shelf alongside the stove itself where things were placed while the cooking was going on. The previous mishnah discussed such a courtyard that was built as one piece with the kirah. Our mishnah takes up the case where the courtyard is a separate piece, standing on its own and not joined physically to the kirah, and it then turns to a second subject entirely: the small feet upon which the kirah rested.
The Mishnah opens: "haytah meforeshet min hakirah, bizman shehigvohah shalosh etzba'ot, mitamei bemaga uve'avir" - if the courtyard was set apart from the kirah and not attached to it, then as long as its rim rises three fingerbreadths, it is regarded as an earthenware utensil in its own right, and it becomes tamei both by direct contact and through its airspace. Earthenware kelim have this distinctive quality: a source of tumah suspended within their inner space renders them tamei even without touching them.
Why does the detached courtyard share the fate of the kirah? Because the two of them serve one function. The courtyard exists for the sake of the cooking done on the kirah, and the halachah looks at how the pieces work rather than only at whether they are cemented to one another. Even without any physical connection, the courtyard is treated as belonging to the kirah, exactly as we find earlier in the masechet regarding the courtyard of an oven. The practical result is that if one of them contracts tumah, the other contracts it as well.
Two situations are then excluded. In the language of the Mishnah, if the ledge is "pachot mikan", lower than that measure, "o shehaytah chalakah", or was perfectly smooth without any raised edge whatsoever, then "tehorah": tumah has no hold on it whatsoever. Such a piece is caught in between and belongs to neither category. On the one hand it was fashioned only to assist the cooking done on the kirah; on the other, it is far too insubstantial to be reckoned a kirah of its own. Lacking the standing of an independent utensil, the halachah leaves it clean.
Pitputei Kirah: The Feet of the Stove
The Mishnah now turns to the status of the little legs at the base of the kirah, the pitputei kirah. The stove was frequently set right down on the ground, but it was fitted with these small feet so that its walls would not rest directly upon the earth. As a rule there were three of them, which is what a stove needs in order to stand steady and balanced.
Regarding these legs the Mishnah rules: "sheloshah shel shalosh etzba'ot, mitam'in bemaga uve'avir". Three legs that measure three fingerbreadths in height belong to the stove itself, so tumah reaches them both by touch and through the air space they enclose. Should a sheretz drop down into the area shut in between the three legs, they contract tumah, and the stove resting upon them is drawn into that tumah as well.
The next clause reads "pachot mikan", legs standing lower than that measure, and of them the Mishnah says "kol shekein hein temei'in": they are susceptible all the more so. The shorter the leg, the more plainly it is nothing beyond a piece of the stove, so it goes without saying that its tumah follows the stove's.
A last point rounds off the Mishnah: "va'afilu hein arba'ah", a stove standing on four legs is no different, and every one of them receives tumah. Since three legs are enough for a stove to stand firmly, one might have argued that a fourth serves no purpose and should be dismissed as insignificant. The Mishnah will not accept that reasoning. No individual leg is singled out as a needless addition to be ignored; the entire set becomes tamei together with the stove.