Date: 10 Adar 5590
From: Rabbi Moshe Sofer
To: Unknown recipient
A self-authored scholarly treatise on three foundational principles of tumas ohel: the Chasam Sofer establishes that transmission of tumah through a tefach opening is d'oraisa (halachah leMoshe miSinai), not merely Rabbinic, critiquing the Shach's contrary position as either a scribal error or narrowly limited; he analyzes the four-way dispute among Rashi, Rivam, Rambam, and Ra'avad regarding kever sasum; and he examines the application of lavud in tumah contexts, concluding with novel observations on small openings and the lavud principle.
Source: Shu"t Chasam Sofer YD §340