Responsa for Shabbat 4:2
טוֹמְנִין בִּשְׁלָחִין, וּמְטַלְטְלִין אוֹתָן, בְּגִזֵּי צֶמֶר, וְאֵין מְטַלְטְלִין אוֹתָן. כֵּיצַד הוּא עוֹשֶׂה, נוֹטֵל אֶת הַכִּסּוּי וְהֵן נוֹפְלוֹת. רַבִּי אֶלְעָזָר בֶּן עֲזַרְיָה אוֹמֵר, קֻפָּה, מַטָּהּ עַל צִדָּהּ וְנוֹטֵל, שֶׁמָּא יִטֹּל וְאֵינוֹ יָכֹל לְהַחֲזִיר. וַחֲכָמִים אוֹמְרִים, נוֹטֵל וּמַחֲזִיר. לֹא כִסָּהוּ מִבְּעוֹד יוֹם, לֹא יְכַסֶּנּוּ מִשֶּׁתֶּחְשָׁךְ. כִּסָּהוּ וְנִתְגַּלָּה, מֻתָּר לְכַסּוֹתוֹ. מְמַלֵּא אֶת הַקִּיתוֹן וְנוֹתֵן לְתַחַת הַכַּר, אוֹ תַחַת הַכָּסֶת:
It is permitted to store in sh'lachin [hides. The targum of (Leviticus 1:6): "And he shall flay" is "Veyashlach."], and they may be moved (on the Sabbath), [whether or not he stored in them, because they can be reclined upon.] (It is permitted to store) in shearings of wool, and it is forbidden to move them, [for they are set aside for spinning and weaving. And even though he stored in them for the time being, he did not renounce them (for spinning and weaving) entirely, not having designated them specifically for storing; but if he did, he may move them.] What can he [the one who stored his pot] do? [How can he take it out if it is forbidden to move them (the shearings), it being entirely covered by them?] He takes off the cover [of the pot, which has the status of a vessel], and they fall off. [And even though they rest upon it, this does not concern us, it not being regarded as a basis for them, its function being to cover the pot.] R. Eliezer b. Azaryah says: He turns the box on its side and takes, lest he take it out and not be able to return it. [When he comes to take (food from the pot), he turns the box (containing the pot) on its side, lest he take the pot, and the shearings on either side fall into the hole (in which the pot is stored), so that if he wishes to return it there, he will not be permitted to move the shearings on either side to fit it back into the hole.] The sages say: He takes it and he returns it. [He takes the pot, and if the shearings on either side do not fall and the hole is not spoiled (for re-storing), he returns the pot to its place; and we do not forbid him to take the pot ab initio lest he spoil the hole. And the sages agree that if the hole were spoiled, he may not return it. The halachah is in accordance with the sages.] If he did not cover it while it was still day, he may not cover it when it gets dark. [For it is forbidden to store on the Sabbath, even in something which does not add heat.] If he covered it, and it became uncovered, he is permitted to re-cover it. One may fill up a kettle and place it [on the Sabbath] under a kar [that he places under his head, even though it is full of mochim or feathers, this not being the usual manner of "storing"], or under a keseth, [larger than a kar].