Mishnah Taharos 9:6: One who leaves one's olives on the roof for them to dry out into pieces [for eating], even if they are [piled as high as] a cubit tall, they are not primed [for impurity, even if they become moistened]. If one put them in the house for them to wither and he intends to bring them up to the roof, or if one put them on the roof for them to wither or to split them, these are thereby primed [for impurity, if they become moistened]. If one put them in the house until he protects his roof [i.e. improves his roof to create a sufficiently protected area in which to keep his olives] or until he moves them to another place, they are not primed [for impurity].

הַמַּנִּיחַ זֵיתָיו בַּגַּג לְגַרְגְּרָם, אֲפִלּוּ הֵן רוּם אַמָּה, אֵינָן מֻכְשָׁרִים. נְתָנָן בַּבַּיִת שֶׁיִּלְקוּ וְעָתִיד לְהַעֲלוֹתָם לַגַּג, נְתָנָן בַּגַּג שֶׁיִּלְקוּ אוֹ שֶׁיִּפְתְּחֵם, הֲרֵי אֵלּוּ מֻכְשָׁרִין. נְתָנָן בַּבַּיִת עַד שֶׁיְּשַׁמֵּר אֶת גַּגּוֹ אוֹ עַד שֶׁיּוֹלִיכֵם לְמָקוֹם אַחֵר, אֵינָן מֻכְשָׁרִין:

Mishnah Taharos 9:7: If one intends to take one pressing or two pressings from them [from olives in the vat], Beit Shammai says: he may cut out [the olives for pressing] in impurity [i.e. with impure hands or utensils, as the olives are not primed to become impure], but he must cover them up [the remaining olives] in purity. And Beit Hillel says: he can even cover them in impurity. Rabbi Yose says: one may dig out [all the olives from the vat] with metal axes and walk them to the olive press in impurity.

רָצָה לִטֹּל מֵהֶן בַּד אֶחָד אוֹ שְׁנֵי בַדִּין, בֵּית שַׁמַּאי אוֹמְרִים, קוֹצֶה בְטֻמְאָה וּמְחַפֶּה בְטָהֳרָה. בֵּית הִלֵּל אוֹמְרִים, אַף מְחַפֶּה בְטֻמְאָה. רַבִּי יוֹסֵי אוֹמֵר, חוֹפֵר בְּקַרְדֻּמּוֹת שֶׁל מַתֶּכֶת וּמוֹלִיךְ לְבֵית הַבַּד בְּטֻמְאָה: