From: Rabbi Moshe Sofer
To: Rabbi Hersh of Aglid
The Chasam Sofer delineates three ascending categories of tevilas mitzvah and analyzes the dispute between the Ra'avad and the Beis Yosef regarding whether separating chafifah from tevilah applies to all women today or only to tevilah at its precise time. He concludes with a novel proof that the Rif holds sechitas se'ar (wringing hair) is halachically permitted, as otherwise the Rif's distinction between personal immersion and vessel immersion on Shabbos and Yom Tov would be internally inconsistent.
Source: Shu"t Chasam Sofer YD §196