At one of those historic sites that litter the east coast, I watched a woman make corn meal with a tree trunk round that had been hollowed to a point and a metal rod. Toss in some dried corn, gravity takes the kernels to the lowest point and proceed to pound with rod. She let me have a go. It didn't take long to make enough meal for corn meal mush for a small family meal.
I wonder how many of the women in the days when that sort of work was common (churning butter with an upright churn, and washing clothes by hand with a plunger use the same motion, albeit with less impact) developed severe arthritis of the upper spine?
While it's absolutely possible to "grind" grain in very low tech ways, it wears people out early.
I have a Corona hand mill, and have used it. It requires several pass throughs to get wheat fine enough for good flour. However, it's much better than my Whisper Mill to make a coarse grind for hot cereal, or to add to bread for texture.
The above mill appears to be able to be run by a v-belt and motor... you probably could rig up a solar set up for it.
We rigged up a way to run our Squeezo strainer off a cheap Harbor Freight 1/2" electric drill, and oh! does that save hours of work, and later of pain! Hubby overdid manual labor most of his life... pounding fence posts, hand digging the entire foundation for a barn, pitching manure every day for 30 heifers... his spine is trashed. Plus, he apparently has no rotator cuff left on either shoulder! He used to voluntarily do most of the heavier work for me, including cranking the Squeezo and the grain mull.
Mechanizing the work allows us to be able to continue doing it into our "golden years"... but it would have made more sense to have done it earlier, and avoided a lot of pain!
Summerthyme