From: Rabbi Moshe Sofer
To: Rabbi Zalman Perles
Rabbi Zalman Perles asks whether one may carry on Shabbos to a mikvah building standing apart from the town. The Chasam Sofer permits it, reasoning that since the tzuras hapesach joins the mikvah to the town's existing majority-standing enclosure, it is not treated as an isolated field.
Source: Shu"t Chasam Sofer OC §88