Mishnah for Kelim 10:1
אֵלּוּ כֵלִים מַצִּילִין בְּצָמִיד פָּתִיל, כְּלֵי גְלָלִים, כְּלֵי אֲבָנִים, כְּלֵי אֲדָמָה, כְּלֵי חֶרֶס, וּכְלֵי נֶתֶר, עַצְמוֹת הַדָּג וְעוֹרוֹ, עַצְמוֹת חַיָּה שֶׁבַּיָּם וְעוֹרָהּ, וּכְלֵי עֵץ הַטְּהוֹרִים. מַצִּילִים בֵּין מִפִּיהֶם בֵּין מִצִּדֵּיהֶן, בֵּין יוֹשְׁבִין עַל שׁוּלֵיהֶן בֵּין מֻטִּין עַל צִדֵּיהֶן. הָיוּ כְפוּיִים עַל פִּיהֶן, מַצִּילִים כֹּל שֶׁתַּחְתֵּיהֶן עַד הַתְּהוֹם. רַבִּי אֱלִיעֶזֶר מְטַמֵּא. עַל הַכֹּל מַצִּילִין, חוּץ מִכְּלֵי חֶרֶס, שֶׁאֵינוֹ מַצִּיל אֶלָּא עַל הָאֳכָלִים וְעַל הַמַּשְׁקִין וְעַל כְּלֵי חָרֶס:
The following vessels protect their contents when they have a tightly fitting cover: those made of cattle dung, of stone, of clay, of earthenware, of sodium carbonate, of the bones of a fish or of its skin, or of the bones of any animal of the sea or of its skin, and wooden vessels that not subject to impurity. They protect whether [the covers close] their mouths or their sides, whether they stand on their bottoms or lean on their sides. If they were turned over with their mouths downwards they afford protection to all that is beneath them to the deep. Rabbi Eliezer declares this impure. These protect everything, except that an earthen vessel protects only foods, liquids and earthen vessels.