I mean the mathematician might be right here. A lot of bathroom scales are for measuring people-sized weights and a (granted, normal-sized) bowel movement would likely not be measured accurately on its own.

If we go with the engineer’s method for an accurate poo-only measurement, we’re going to need in involve a set of kitchen scales somewhere. This adds a further complication : does this person shit in the kitchen or do we bring the kitchen scales into the bathroom.

I may be thinking too much about this.