Ohalos5: 2
אֲרֻבָּה שֶׁבֵּין הַבַּיִת לָעֲלִיָּה וּקְדֵרָה נְתוּנָה עָלֶיהָ. וּנְקוּבָה בְכוֹנֵס מַשְׁקֶה. בֵּית שַׁמַּאי אוֹמְרִים: הַכֹּל טָמֵא. וּבֵית הִלֵּל אוֹמְרִים: הַקְּדֵרָה טְמֵאָה וַעֲלִיָּה טְהוֹרָה. רַבִּי עֲקִיבָא אוֹמֵר: אַף הַקְּדֵרָה טְהוֹרָה:
There is an opening between the lower story and the upper story of a house that has been covered by a pot. [The pot has] a crack large enough for liquid to seep in. Beis Shammai say: Everything [in the house] becomes tamei. Beis Hillel say: The pot becomes tamei, but the upper story remains tahor. R’ Akiva says: Even the pot re-mains tahor.