Mishnayos Yadayim Perek 2 Mishnah 1

נטל את ידו משטיפה אחת – we call it one rinsing all the while that he didn’t pour other than on one hand until the joint/wrist, and it is sufficient once with his one hand, even though there isn’t in the vessel one-quarter of a LOG other than it comes from the remnants of purity. But for both of his hands, even though they come from the remnants of purity, they are not effective until he pours twice. The first [rinsing] until the joint/wrist and the second time up until the joint/wrist. But Maimonides explains: from one pouring is from one rinsing [of water on his hands]. But when he pours both of his hands with one rinsing, the waters become defiled on his one hand, and it is found hat he washes the second with water that became defiled, and his hands were not purified until he poured a second [rinsing] of water from one-quarter of a LOG. But when he pours [water] on only one hand, through that rinsing, his hand is purified, but when he pours water a second time to purify the water that is on his hand, it is sufficient with less than one-quarter of a LOG. But the Halakha is not according to Rabbi Meir.

נפל ככר של תרומה – where he poured the first waters from one-quarter of a LOG [of a single rinsing] and a loaf of heave-offering/Terumah fell up upon them, or a loaf of heave-offering came in contact with the waters that were on his hand prior to his drying them, or prior to his pouring upon them a second time [for consuming heave-offering].

טהור – for just as they are effective to purify his hands, they are also effective to purify themselves.

ר' יוסי מטמא – for he holds that they are effective to purify his hands, but they themselves are impure.