"A Dangerous Time is Not a Proof" in the Tosefta

"A man who had a seminal emission (Baal Keri) who does not have water to dip in may read the Shema, but he may not [read it loud enough so that he can] hear [himself talking] with his own ear, and does not say the Beracha (blessing) not before it and not after it.” [These are] the words of Rebbi Meir.

And the Chachamim (Sages) say, ”He may read the Shema and he may [read it loud enough so that he can] hear [himself talking] with his own ear, and he says the Beracha [both] before it and after it.”

Rebbi Meir said, “One time we were sitting in the Bet Midrash (Study Hall) in front of Rebbi Akiva and we were reading the Shema, but we were not saying it loud enough to be able to hear ourselves, because of one inquisitor who was standing by the door.”

They (i.e. Chachamim) said [back] to him, “The time of danger is not a proof.”

"They can be covered with planed boards," the words of R. Yehudah.

The sages say: "They are prohibited unless there is sufficient space between them."

R. Yehudah says: "It once happened that at the time of [religious] danger they set up ladders, covered them with boards, and slept under them."

They said to him: "A time of danger is no proof [for a normal case]."

But all agree that even if the boards be four handbreadths wide there must be between them sufficient space.