It may not be a myth but no one has turned up any evidence that it is true. Ice cream in the modern sense--a frozen custard churned during freezing--is not known to have existed before that time. The first published recipes came out of France, though of course, the French cribbed many of their best ideas from others.
Before Nancy Johnson's machine, the churning was done laboriously by hand.
Before Nancy Johnson's machine, the churning was done laboriously by hand.