“A mortar was made by burning out a stump, and the corn was crushed in it by a heavy weight.” From: Stories of pioneer life, for young readers. Boston: D.C. Heath & Co. 1900. Page 123.
A samp mortar is a tool for grinding dried corn (maize.) The resultant ground cornmeal product would be called “samp.”
The tool was made from the stump of a tree (ideally, white oak or pine) burned hollow, scraped clean and polished. You aimed to make your hollow an inverted conical shape — the fire could be guided by holes drilled in the stump.
Ideally, the tree stump would have nearby a healthy sapling tree, or a strong but flexible tree branch. If so, you’d tie a block of white oak to the sapling or branch.
Otherwise, you’d make a sweep coming off a post and hang the pounder off that.
You worked the device like a piston, with whatever you’d hung the pounder on acting as a spring to lift it back up for you to ease the work. Still, it could take half a day to grind up half a bushel of corn into cornmeal.
They were used in Canada and in the United States. Some small towns would make a public one for everyone to use in the public square.
‘[The corn] was then pounded in a mortar—the hollowed-out end of a stump. The pestle might be worked by hand entirely, or it might be suspended from the end of a long pole that pulled it up after each downward stroke.’ From: “The story of agriculture in the United States”. Albert Hart Sanford. (Boston: D.C. Heath & Co. 1916.) Page 124.