Tossefta sur La Genèse 1:20

Kohanim sanctify their hands in the Temple until the "joint" (i.e., the wrist, see Hul. 106b:1), and their feet until the [bottom of the] calf. One who pours over his hands shall not say, "Since the first waters were impure, behold, I am pouring from the impure"^* translation follows the GR"A, and if he did so, he must dry off his hands [and wash again]. One who immerses his hands does not need to dry them off. One who pours over his hands needs to raise up his hands so that the water does not run beyond the joint (i.e., back toward the hand), for [otherwise] it will return [to the hands] and will defile his hands, but one who immerses his hands does not need to raise up his hands. One who pours over his hands -- if he intended [to purify them], his hands are pure. Rabban Shimon ben Gamaliel says, [if] he poured the first [waters] and afterwards found a fly on his hands, or any other [creature] whose creation was from the water (see Gen. 1:20), his hands are pure. One who pours over his hands -- if the water flowed until the joint, his hands are pure, and if not, his hands are impure. [If] there is a doubt [as to whether the water] flowed [to the wrist], his hands are pure, and Rabbi Yosei says, his hands are impure.