And it’s been invented again.
A fellow from Alaska recently sent me a “Hole Maker” or as he called it a “Circular Contained Earth Extractor”. It’s a 2 inch water pipe about 8 inches long. It is slit up the side and cut at an angle on one end. There is a rod welded to the non-pointed end for driving it into the ground. When you pull it out, the dirt stays inside of it. It works fine in clean soil. But hit a little rock with it, and you’re done for.
I’m not really a gadgeteer. I’ll stick to the trowel.