I had to get out my copy to remind myself of the author of The Bathroom, Alexander Kira. From a review of the three major appliances in Treehugger,
https://www.treehugger.com/bathroom-...-plumbing.html
This work was done in 1966. Recently, a 'butt-load' of money was made with the Squatty Potty, which draws on this research.
https://www.squattypotty.com/