Terumot, Chapter Four, Mishnah Seven
I have already explained on several occasions that if terumah falls into non-sacred produce it renders the entire mixture medumma. Medumma is doubtful terumah and it can only be eaten by a priest. However, if the amount of non-sacred produce was large enough, the terumah can be removed, given to a priest and the rest of the mixture returns to being non-sacred produce. This is obviously a much better scenario for the person who owns the mixture because he can eat all of the hullin. Our mishnah teaches how much non-sacred produce there must be in relation to the amount of terumah that fell in.
1) Rabbi Eliezer says: terumah can be taken out [if it falls into] a hundred and one parts.
2) Rabbi Joshua says: in a hundred and more, and this more has no definite measure.
3) Rabbi Yose ben Meshullam says: this more must be a kav to a hundred seahs, a sixth [of the seah] which renders the whole as medumma.
Section one: According to Rabbi Eliezer there must be a full one hundred parts non-sacred produce (hullin) for every part terumah. So if one seah of terumah falls into one hundred seahs hullin, there will be a total of 101 seahs, and the terumah can be removed. One seah is given to the priest and the rest reverts back to hullin.
Section two: Rabbi Judah holds that if one seah of terumah falls into 99 seahs and a little bit more of hullin, thereby making a mixture that has a total of 100 parts and a little bit more, the terumah can be taken out. This more, the amount over 99 seahs, can be of any amount, even the smallest amount.
Section three: Rabbi Yose ben Meshullam agrees in principle with Rabbi Joshua, but says that there is a measure to this small amount. In the situation described above, where one seah of terumah falls into a vat of hullin, there must be 99 seahs and one kav of hullin in order for the terumah to be nullified. The kav is 1/6 of the seah of terumah that fell in. In other words, the extra amount must be 1/6 of the amount of terumah that one is attempting to nullify.