IIRC there was a “This Old House” episode once where Rich Trethewey took a tour of the Kohler factory in Wisconsin, including their test facility. They used a variety of substances, all of which had to completely pass through in one flush. The ones I remember were cut sections of rubber garden hose (representing compacted stools, apparently), and ping pong balls (representing floaters, I presume).
I am reminded of the dialogue between Dr. Kellogg and his patient, in that crazy movie “The Road To Wellville”
-Dr. Kellogg: “Your stools are small and foul smelling…mine are large and smell like fresh-baked bread!”
Patient:“Why is that doctor?”
-Dr. Kellogg: “because I abstain from meat and eat only vegetable foods!”
A weird movie but a lot of fun!