Tevul Yom 1:3-4

T’vul Yom 1:3

Regarding the knob on the back of a loaf, a small piece of salt or burnt crust smaller than a fingerbreadth, Rabbi Yosi says that whatever is eaten with the loaf is rendered unclean by a t’vul yom, and it goes without saying that this is so with other sources of impurity.

T’vul Yom 1:4

Regarding a pebble in a loaf, a large piece of salt, a lupine in a loaf or burnt crust larger than a fingerbreadth, Rabbi Yosi says that whatever isn’t eaten with the loaf isn’t rendered unclean even by an av hatuma (a “father of impurity”) and it goes without saying that this is so for a t’vul yom.