Mishnah Taharos 9:4: One who finishes [harvesting] his olives, but leaves one remaining basket [and does not put it in the vat], he should place it in [the vat] before the eyes of a priest [i.e. so the priest can observe it as it is primed for impurity, and ensure that it does not become impure], according to Rabbi Meir. Rabbi Yehuda says: he should bring the key [to his olive press to a priest] immediately [but the priest does not have to be observing the whole time]. Rabbi Shimon says: [he should bring him they key] from hour to hour [i.e. bringing the key within twenty-four hours is sufficient].

הַגּוֹמֵר אֶת זֵיתָיו וְשִׁיֵּר קֻפָּה אַחַת, יִתְּנֶנָּה לְעָנִי הַכֹּהֵן, דִּבְרֵי רַבִּי מֵאִיר. רַבִּי יְהוּדָה אוֹמֵר, יוֹלִיךְ אֶת הַמַּפְתֵּחַ מִיָּד. רַבִּי שִׁמְעוֹן אוֹמֵר, מֵעֵת לְעֵת:

Mishnah Taharos 9:5: One who leaves olives in the press for them to soften to be easier to press, they are thereby primed [for impurity, by the liquid that emerges from them]. If [one left olives in a press] for them to soften to be salted, Beit Shammai says: they are primed [for impurity]; and Beit Hillel says: they are not primed. One who crushes olives with impure hands has rendered them impure.

הַמַּנִּיחַ זֵיתִים בַּכּוֹתֵשׁ שֶׁיִּמְתֹּנוּ שֶׁיְּהוּ נוֹחִין לִכְתֹּשׁ, הֲרֵי אֵלּוּ מֻכְשָׁרִים. שֶׁיִּמְתֹּנוּ שֶׁיִּמְלָחֵם, בֵּית שַׁמַּאי אוֹמְרִים, מֻכְשָׁרִים. וּבֵית הִלֵּל אוֹמְרִים, אֵינָן מֻכְשָׁרִים. הַפּוֹצֵעַ זֵיתִים בְּיָדַיִם טְמֵאוֹת, טִמְּאָן: