Mix the warm mashed potatoes and sugar together; then add the flour; next, add the six cupfuls of boiling water, poured on slowly: this cooks the flour a little. It will be of the consistency of batter. Let the mixture get almost cold, stirring it well, that the bottom may become cool also. It will spoil the yeast if the batter be too hot. When lukewarm, add the tea-cupful of yeast. Leave this mixture in the kitchen, or in some warm place, perhaps on the kitchen - table (do not put it too near the stove), for five or six hours, until it gets perfectly light. Do not touch it until it gets somewhat light; then stir it down two or three times during the six hours. This process makes it stronger. Keep it in a cool place until needed.
This yeast will last perpetually, if a tea-cupful of it be always kept, when making bread, to make new yeast at the next baking. Keep it in a stone jar, scalding the jar every time fresh yeast is made.
In summer, it is well to mix corn-meal with the yeast, and dry it in cakes, in some shady, dry place, turning the cakes often, that they may become thoroughly dry. It requires about one and a half cakes (biscuit-cutter) to make four medium-sized loaves of bread. Crumb them, and let them soak in lukewarm water about a quarter or half an hour before using.