>>3085767multiple springs coiling up other springs.
But to be serious. There are watches that are powered by a weighted wheel that spins via the movement of the wearer and coils up the main spring of the watch. Sensei moves, so that's possible.
But to be honest with you, I rather think it's something more modern or something I haven't even thought of. It might as well be the feeling of love or faith that powers Sensei.