The Talmud, by Joseph Barclay, , at sacred-texts.com
1. "With what may they cover up (pots to retain the heat)?" "And with what may they not cover them up?" "They may not cover them up with oil-dregs, or dung, or salt, or lime, or sand either fresh or dry, or straw, or grape-skins, or woollen, or herbs when they are fresh, but they may cover up with them when they are dry. They may cover up with garments, and fruits, with doves wings, with carpenters sawdust, and with tow of fine flax." Rabbi Judah forbids "fine," but allows "coarse."
2. They may cover up with hides, and remove them,with woollen fleeces, but they must not remove them. "How does one do?" "He takes off the cover, and they fall down." Rabbi Eleazar, the son of Azariah, says "the vessel is inclined on its side, and he takes them away." "Perhaps he took them away and cannot return them?" 1 But the Sages say "he may take them away, and return them." "He does not cover it, while it is yet day?" "He must not cover it, when it begins to be dark." "He covered it, and it opened?" "It is allowed to cover it again." A man may fill the goblet, and put it under the pillow or under the bolster (to warm it).
88:1 As that would involve "labour."