Tosefta (Zavim 2:9): What is Kever ha'Tehom? A Mes was buried in straw, earth and pebbles. However, if it was buried in water, a totally dark place or a crevice in a rock, [since with difficulty one can see it, e.g. through a torch], it does not make Kever ha'Tehom.

The general rule is, any case in which you can (i.e. it is destined to) clear away [and buried elsewhere], it makes Kever ha'Tehom. Any case in which you cannot (are not destined to) clear it away, it does not make Kever ha'Tehom.

Question: Is straw not destined to be cleared away? Is the Tosefta unlike R. Yosi?

(R. Yosi): If there was straw [over a Mes] and he was Mevatel it (decided to leave it there permanently), it is Batel. (Stam, i.e. without Bitul, we do not say that it is destined to be cleared away, so it is as if there is air over it!)

Answer (R. Yosi bei R. Bun citing Rav Chisda): [The Tosefta] is like everyone. R. Yosi discussed when he mixed [the straw] with earth. (Then, Stam it is destined to be cleared away.)

Rebuttal: [R. Yosi says] there is straw that is like earth, and earth that is like straw. (This shows that he discusses Stam straw.)

Straw that is not destined to be cleared away, it is like earth. Earth that is destined to be cleared away, it is like straw;

(D'Vei R. Yanai): If one covered [straw] with mats, it is Batel. (He will leave both of them there.)

Question: See [this is unreasonable]! If one filled [the house] with mats, it is not Batel (presumably, he will remove them). If one covered [straw] with mats, it is Batel?!

Question: If one filled [the house] with date branches, this is a question [whether they are Batel].

(R. Zerikan citing R. Ami citing Reish Lakish): Even [if he covered it with] spit (this is considered a covering).

What is Kever ha'Tehom? It is any [grave] that no one remembers.

Question: You should be concerned lest someone at the end of the world remembers it (e.g. the one who buried him), and the Chazakah of [one who was] alive is that he is still alive!

Answer: The case is, he found it Kamtzutz (his legs by his head. Surely he was not buried, rather, a rockpile fell on him.)

(Beraisa): Nothing makes Kever ha'Tehom, except for a Mes.

Question: A Neveilah, a Kal v'Chomer [teaches that also it makes Kever ha'Tehom]!

A Mes is Metamei b'Ohel, yet [it has the leniency that] it makes Kever ha'Tehom. A Neveilah is not Metamei b'Ohel. All the more so it should make Kever ha'Tehom!

Answer: Why was it said 'nothing makes Kever ha'Tehom, except for a Mes'? It excludes [a Zav after he immersed on day seven; he makes] Mishkav u'Moshav. (If he will see an emission today, he is still Tamei. We do not say that since no one knows now, he is not Metamei Mishkav u'Moshav. Rather, what he sits on is Taluy; if he sees, it was Tamei from when he sat on it. We explained this like PNEI MOSHE.)

Question (R. Yosi bei R. Bun): Bar Pikah asked Rebbi [our Mishnah discusses only] a cave with a roof. (It is considered to be filled, so it is as if the Tum'ah rests.) Is it even a cave without a roof?! (If so, it is Safek Tum'ah floating on the water, which is always Tahor!)

Remark: Bar Pikah thinks that Safek Tum'ah floating on the water [is Tahor even regarding Tum'as Mes].

Answer (Rebbi): Bar Pikah is still in his folly. Safek Tum'ah floating on the water is Tahor only for a Sheretz, but for a Mes, it is as if [the Tum'ah] stands [even if there is no roof. We explained this like GILYONEI HA'SHAS];

This is like it was taught, anything thrown [and it is a Safek whether or not they touched a Tahor person or Kli], the Safek is Tahor, except for a k'Zayis of a Mes, and all [Taharos that were thrown and perhaps] towered [above Tum'as Mes], and anyone who is Metamei (Kelim made to sit or lie on) below and above (e.g. a Zav or Zavah. We explained this like R. SHIMSHON Taharos 4:3.)

Question: (Our Mishnah says that if Tum'ah was found buried in the floor of the cave, if he immersed from Tum'as Mes, he is Tamei.) Does it argue with R. Yoshiyah? R. Yoshiyah said that if Tum'ah is buried in the ground under a house, a Nazir does not shave [for it]!

Answer #1 (R. Yochanan): Here (R. Yoshiyah) discusses when [the Tum'ah] is to the side. (A Nazir does not shave for being under the same roof as it.) Our Mishnah teaches when he was directly over [the Tum'ah - OHR YAKOV].

Answer #2 (R. Ezrah citing R. Yudan): You can even say that in both cases it is to the side, or in both cases it is directly over it. What [does our Mishnah mean] 'he is Tamei'? He is Tamei, but he does not shave.