Reference for Eduyot 1:7
בֵּית שַׁמַּאי אוֹמְרִים, רֹבַע עֲצָמוֹת מִן הָעֲצָמִים, בֵּין מִשְּׁנַיִם בֵּין מִשְּׁלֹשָׁה. וּבֵית הִלֵּל אוֹמְרִים, רֹבַע עֲצָמוֹת מִן הַגְּוִיָּה, מֵרֹב הַבִּנְיָן אוֹ מֵרֹב הַמִּנְיָן. שַׁמַּאי אוֹמֵר, אֲפִלּוּ מֵעֶצֶם אֶחָד:
Beth Shammai say: A quarter [of a kav] of the bones [of the dead], whether from two or three, [cause tent-uncleanliness. And fewer than a quarter cause uncleanliness only by touching or carrying, but not in a tent. And Beth Shammai hold that a quarter of a kav cause tumah (uncleanliness) even if they are from many dead.] And Beth Hillel say: A quarter (of a kav) of the bones of the body. [That is, from the body of one dead man and not from many dead. And, even from one dead man, there is no tumah unless there be in the quarter of a kav either] the majority of the built [i.e., the majority of the built of the body] or the majority of the number [of the bones of a man — one hundred and twenty-five, a man's bones numbering two hundred and forty-eight.] Beth Shammai say: Even one bone. [i.e., If one bone of the dead man fills a quarter of a kav, it causes tent-uncleanliness. The halachah is in accordance with Beth Hillel.]