Date: Erev Sukkos 5599
From: Rabbi Moshe Sofer
To: Rabbi Yosef
The Chasam Sofer rules that inspecting only three blisters is insufficient and every blister must be individually examined, drawing an analogy from the laws of niddah where all particles must be checked. When blisters are numerous and evidence is lost without inspection, the organ's presumption of health is undermined and stringency is required even in cases of financial loss.
Source: Shu"t Chasam Sofer YD §49