A pit that has a place in it for a pot to be set is tamei. And [a pit] of glassmakers, if it has in it a place for a pot to be set, it is tamei. A furnace of lime manufacturers, or [a furnace] of glassware manufacturers, or [a furnace] of potters, is tahor. A purnah, if it has a rim, it is tamei. R’ Yehudah says: If it has istigios [it is tamei]. Rabban Gamliel says: If it has a thin lip [it is tamei].