Tosefta על נזיר 50:10

One who eats from the carcass of a clean fowl, from the bones, or from the sinews, or from a clutch of eggs, from the blood or the meat of a living animal is pure. From the ovary of its eggs, from the craw, or from the the intestines, or [if] he melted the heart (alt., the "fat" (Beitzah 7a:9)) and swallowed it, he is impure. [If] he wrapped it up (karcha) in lettuce and swallowed it, it is impure. [If he wrapped it] in bast (cf. Pes. 115b:6) and swallowed it, he is pure. [If] he vomited it and it stayed in the place of swallowing (i.e., the throat), it defiles one [degree] and renders unfit [one degree]. [If] he vomited it and went back and swallowed it again, and it stayed in the place of swallowing, he defiles one [degree] and renders unfit [one degree]. [If] he swallowed it and it did not have at least an olive's bulk, he is completely pure. [If] he took a bird and ate it: If it has at least an olive's bulk, he is impure, and if not, he is pure.