Mishnah Yadayim 1:1: A quarter [of a log, a specific unit of volume] of water is to be poured onto the hands, for [the ritual washing of the hands for] one person, and even for two. Half of a log [is to be poured from] for three or four. And from [a vessel containing] one log [of water], five or ten or even one hundred [people may wash their hands]. Rabbi Yose says: but only provided there not be less than a quarter [of a log remaining] for the last one of them [to wash]. One may add [water, by pouring it onto the hands past where it had fallen] on the second [pouring of water; i.e. on a third pouring, one can pour past where the waters fell on the second pouring]. But one may not add on the first [pouring; i.e. on the second pouring, one may not pour past where the waters fell on the first pouring].

מֵי רְבִיעִית נוֹתְנִין לַיָּדַיִם, לְאֶחָד, אַף לִשְׁנַיִם. מַחֲצִית לֹג, לִשְׁלשָׁה אוֹ לְאַרְבָּעָה. מִלֹּג, לַחֲמִשָּׁה וְלַעֲשָׂרָה וּלְמֵאָה. רַבִּי יוֹסֵי אוֹמֵר, וּבִלְבַד שֶׁלֹּא יִפְחֹת לָאַחֲרוֹן שֶׁבָּהֶם מֵרְבִיעִית. מוֹסִיפִין עַל הַשְּׁנִיִּים וְאֵין מוֹסִיפִין עַל הָרִאשׁוֹנִים:

Mishnah Yadayim 1:2: One may pour [water for washing] onto the hands from all [kinds of] vessels, even from vessels of bovine dung, from vessels of stone, or from earthen vessels. One may not pour [water for washing] onto the hands out of the sides of vessels [i.e. from vessel fragments], nor using the [broken off] bottom of a large jug, nor using the bung of a cask, nor may one pour [water] onto [the hands of] his fellow out of the hollow of his [own] hand, since one may only fill, sanctify, or sprinkle the chatat waters [the waters containing the ashes of the red heifer, used as part of the purification ritual] with a vessel, nor may one take them into one's hands. And nothing can be preserved [from being rendered impure, in cases of an impurity caused by being overshadowed by an enclosed area containing an Origin of impurity] by means of a tight seal [which can sometimes protect against an overshadowing impurity], unless it is [contained within] a [whole] vessel. And something can only be preserved from [being rendered impure by an impure object contained beside it within] an earthenware vessel if it is itself a vessel.

בְּכָל הַכֵּלִים נוֹתְנִין לַיָּדַיִם, אֲפִלּוּ בִכְלֵי גְלָלִים, בִּכְלֵי אֲבָנִים, בִּכְלֵי אֲדָמָה. אֵין נוֹתְנִין לַיָּדַיִם, לֹא בְדָפְנוֹת הַכֵּלִים, וְלֹא בְשׁוּלֵי הַמַּחַץ, וְלֹא בִמְגוּפַת הֶחָבִית. וְלֹא יִתֵּן לַחֲבֵרוֹ בְחָפְנָיו, מִפְּנֵי שֶׁאֵין מְמַלְּאִין וְאֵין מְקַדְּשִׁין וְאֵין מַזִּין מֵי חַטָּאת וְאֵין נוֹתְנִים לַיָּדַיִם אֶלָּא בִכְלִי. וְאֵין מַצִּילִין בְּצָמִיד פָּתִיל אֶלָּא כֵלִים, שֶׁאֵין מַצִּילִין מִיַּד כְּלִי חֶרֶשׂ אֶלָּא כֵלִים: