This isn't the exact video I was looking for, but it's close enough. There was one with a gentleman that had a furnace similar to this and off to the side, using the radiant heat from the furnace pots was a small annealing area where he'd put finished work. The earthen materials used to construct the whole thing gave enough insulation to provide a kiln like enclosure that would hold the temperature close enough.
http://www.youtube.com/watch?v=wvxBjgxOW7c
edit: I think this is the one I was looking for:
http://www.youtube.com/watch?v=ajoGFeuru0o