When I was a kid (almost 40 years ago) the family we went camping with had this setup. A toilet that that put over a long drop, and when you sat on the seat the

When I was a kid (almost 40 years ago) the family we went camping with had this setup. A toilet that that put over a long drop, and when you sat on the seat the the pressure would open the inner seat, effectively splitting it in two and pulling it away to open the hole below. I’d assumed it was some standard pro camping kit. By no amount of searching just now has been able to turn up a device like I’m trying to describe!