The fermentation period for bread made with dry yeast may be shortened if the following yeast ferment is first prepared:
Crumble yeast and soften in 1/2 cup water. Wash, pare, and boil potato in 3 1/2 cups water. Drain potato. Save potato water. Mash potato and add sugar and salt. Cool to lukewarm. Add yeast, and potato water. If necessary add water to make 1 quart of the mixture. Cover unused portion may be stored in the refrigerator and kept for several days.
The Household Searchlight - 1941