From 'Memoirs of an Oregon Moonshiner' by Ray Nelson, 1976...

...Then we had what we called the 'good luck' keg. We took a new ten-gallon keg with nine gallons of one hundred and twenty proof whiskey in it and drove the bung in tight. We then fastened the keg in a wooden frame across the center of each end of the keg and a half-inch by eight-inch bolt protruding from the center of each stick. We set two posts in the ground wide enought apart for the keg to fit between them, with the bolts resting in a notch on top of each post. We then took a leather strap long enough to go around the keg and riveted tin cans onto it, three inches apart and with one side cut out. We buckled the strap tightly around the keg and piped the warm overflow water from the cooling barrel onto it.

The weight of the water in the cans kept the keg rolling. It worked on the same principle as a water wheel. The warm water kept the liquor warm, and the rolling motion aged it faster than had it been sitting still. We kept the keg there until the run was all over with, which sometimes took three or four months. When we finally took the keg down and opened it, the whiskey was a very dark red color and really mild tasting - but don't get fooled on it. One jigger was all you wanted to drink at a time if you wanted to stay on your feet. I have seen fellows scoff at it and say it had very little proof. They didn't scoff long if they drank more than one small glass. It would test about one hundred and seventeen proof.'

Probably be easy to do something ,smaller, like this today with small solar motors and a small solar oven in your backyard. Let the sun make it roll, and the heat from the solar box would do its thing. A few months later, for no money, the same thing should happen, right?