Mishnah Mikvaos 1:1: There are six levels of mikvaot [gatherings of water collected by natural means and immersed in for purification], each [subsequent] one higher than the other: [The first and lowest level is] water collected in shallow pools [in the ground]. If an impure person drank [from one], and a pure person drank [from it afterwards], he is impure. If an impure person drank, and someone filled up a pure vessel [from those waters afterwards], it [the vessel] is impure. If an impure person drank, and then loaf of terumah fell in, if one rinsed [the loaf], it is impure; and if one did not rinse it, it is pure.

שֵׁשׁ מַעֲלוֹת בַּמִּקְוָאוֹת, זוֹ לְמַעְלָה מִזּוֹ, וְזוֹ לְמַעְלָה מִזּוֹ. מֵי גְבָאִים, שָׁתָה טָמֵא וְשָׁתָה טָהוֹר, טָמֵא. שָׁתָה טָמֵא וּמִלֵּא בִכְלִי טָהוֹר, טָמֵא. שָׁתָה טָמֵא וְנָפַל כִּכָּר שֶׁל תְּרוּמָה, אִם הֵדִיחַ, טָמֵא. וְאִם לֹא הֵדִיחַ, טָהוֹר:

Mishnah Mikvaos 1:2: If one filled an impure vessel [from water collected in such pools], and a pure person drank [from it], he is impure. If one filled using an impure vessel, and then filled a pure vessel [with the waters from the first vessel], it is impure. If one filled an impure vessel, and then a loaf of terumah fell in [the pool], if one rinsed it, it is impure; and if one did not rinse it, it is pure.

מִלֵּא בִכְלִי טָמֵא וְשָׁתָה טָהוֹר, טָמֵא. מִלֵּא בִכְלִי טָמֵא וּמִלֵּא בִכְלִי טָהוֹר, טָמֵא. מִלֵּא בִכְלִי טָמֵא וְנָפַל כִּכָּר שֶׁל תְּרוּמָה, אִם הֵדִיחַ, טָמֵא. וְאִם לֹא הֵדִיחַ, טָהוֹר: