Mishnah Taharos 3:2: Rabbi Meir says: Oil is always primary [in its impurity, i.e. of a first degree level, even if it congeals into a solid]. The sages say: even honey. Rabbi Shimon Shezuri says: even wine. A clump of [impure] olives which fell into an oven and it was lit, if [the olives are] exactly the equivalent of an egg [in volume], it [the oven] is pure [since foods cannot render a vessel impure]; if they are greater than the equivalent of an egg [in volume], it is impure, since once the first drop came out, it [that drop of liquid] was rendered impure by the [remaining] egg's volume [which is a sufficient amount of food to render impurity, and that impure drop then renders the oven impure; but when there is exactly an egg's volume of olives, the first drop of it that melts into liquid is not rendered impure by it, since there is no longer a sufficient measure of food left to render it impure]. If they [the impure olives] are separated [from one another], even if there is a se'ah [a large measure] of them, it [the oven] is pure.

רַבִּי מֵאִיר אוֹמֵר, הַשֶּׁמֶן תְּחִלָּה לְעוֹלָם. וַחֲכָמִים אוֹמְרִים, אַף הַדְּבָשׁ. רַבִּי שִׁמְעוֹן שְׁזוּרִי אוֹמֵר, אַף הַיָּיִן. וְגוּשׁ שֶׁל זֵיתִים שֶׁנָּפַל לְתַנּוּר וְהֻסַּק, כַּבֵּיצָה מְכֻוָּן, טָהוֹר. יוֹתֵר מִכַּבֵּיצָה, טָמֵא, שֶׁכֵּיוָן שֶׁיָּצָאת טִפָּה הָרִאשׁוֹנָה, נִטְמֵאת בְּכַבֵּיצָה. אִם הָיוּ פְרוּדִין, אֲפִלּוּ הֵן סְאָה, טָהוֹר:

Mishnah Taharos 3:3: An individual rendered impure through contact with a dead body, who squeezed olives or grapes, if [the fruits he squeezed were] equivalent to exactly an egg [in volume], it [the liquid coming out of them] is pure, as long as he does not touch the part of the [fruit that was already squeezed into] liquid. [If they are] more than the equivalent of an egg [in volume], it is impure, since once the first drop emerged it was rendered impure by an egg's volume [of fruit, which is a sufficient amount to render impurity; but when there is only exactly an egg's volume of fruit, the first drop that emerges is not rendered impure by it, since there is no longer a sufficient measure of food left to render it impure]. If the individual was a zav or zava [a male or female, respectively, with a genital discharge that renders them an Origin of impurity], even with [the squeezing of] one berry, it [the liquid from the fruit] is impure, since when the first drop emerged it became impure through carrying [since a zav/zava also renders impure anything he or she carries or moves]. A zav who milked a goat, the milk is impure, because when the first drop emerged, it became impure through carrying.

טְמֵא מֵת שֶׁסָּחַט זֵיתִים וַעֲנָבִים, כַּבֵּיצָה מְכֻוָּן, טָהוֹר, וּבִלְבַד שֶׁלֹּא יִגַּע בִּמְקוֹם הַמַּשְׁקֶה. יוֹתֵר מִכַּבֵּיצָה, טָמֵא, שֶׁכֵּיוָן שֶׁיָּצְאָה טִפָּה הָרִאשׁוֹנָה, נִטְמֵאת בְּכַבֵּיצָה. אִם הָיָה זָב אוֹ זָבָה, אֲפִלּוּ גַרְגֵּר יְחִידִי, טָמֵא, שֶׁכֵּיוָן שֶׁיָּצְאָה טִפָּה הָרִאשׁוֹנָה, נִטְמֵאת בְּמַשָּׂא. זָב שֶׁחָלַב אֶת הָעֵז, הֶחָלָב טָמֵא, שֶׁכֵּיוָן שֶׁיָּצְאָה טִפָּה הָרִאשׁוֹנָה, נִטְמֵאת בְּמַשָּׂא: