From: Rabbi Moshe Sofer
To: Rabbi Avraham
The Chasam Sofer addresses whether the three-day waiting period before a bloodletting scab becomes a chatzitzah is measured as three full 24-hour periods (me'es le'es) or whether miktzas hayom k'kulo applies. He concludes that since blood-drying is a time-dependent physical process rather than one governed by the solar cycle, me'es le'es is logically required; however, since rivda d'kusilta constitutes only rabbinic-level chatzitzah, one who is lenient and relies on miktzas hayom k'kulo has not erred, while one who is stringent will be blessed.
Source: Shu"t Chasam Sofer YD §190