I was reading a 1901 cookbook today and found a recipe for what sounds like sourdough starter. "Boil two ounces of the best hops in four quarts of water for half an hour, then strain and let stand until lukewarm. Put in an earthen bowl, add half a cup each of salt and brown sugar.... etc., etc..." The recipe concludes by saying "this hops yeast ferments itself and does not need the aid of other yeast....will keep for up to two months and can be used to make excellent bread." Anyone heard of this?