Years ago I worked in a shop that made Smudge Pots, it was owned by the same family that owns Schlosser Forge.
All the Presses, and the lathe's, and a few of the mills were all powered by an overhead belt system just as you see in that video. The power was supplied by a big motor though not Steam like in the video.
To stop the power to one of the presses or other machines, we had a long bar (about 9 - 10 feet) and we would use it to run the belt off the pully, and run the belt back on to supply power; the overhead never stopped turnning.
Crazy stuff, OSHA would have field day with a shop like that in this day and age.
I learned a lot there, no computers to do stuff for you. :wink: