Date: Purim
From: Rabbi Akiva Eiger
To: Unknown recipient
Rabbi Akiva Eiger addresses three analytical questions raised by his son-in-law regarding the Mishnah in Megillah that lists differences among Sifrei Torah, Tefillin, and Mezuzos. He resolves the first question by citing the Ran's explanation that tollin is not truly a distinction between the items; for the second, he offers a novel distinction that writing a Mezuzah on two hides is a disqualification in the writing itself rather than in the surface, preserving the Yerushalmi's question even according to Tosfos; for the third, he notes that the Chavos Yair independently raised the same difficulty regarding Rashi's ruling that Mezuzos require sewing.
Source: Shu"t Rabbi Akiva Eiger §213