Question

Hi,
I am studying The Feynman Lectures on Physics Vol. 1 Chapter 1 on Conservation of Energy. But I am at a loss to understand what Prof. Feynman meant by reversible machine when he's talking about perpaetual motion. Is the reversible machine itself in perpetual motion, but he proves with the help reversible and normal machine that perpetual motion does not exist (Y not greater than X). I'm also confused when he says that a reversible machine if will lift the weight of three by lowering a weight of one, then it'll also lift nearly the weight of one the same amount by lowering the weight of thr