From 1910:
An ancient and honorable recipe.
Peel and boil six medium-sized potatoes. Put them on in cold water, and with them a cheesecloth bag containing a teacupful of hops. There should be two quarts of water. When the potatoes are soft, fish them out with a slit spoon or a perforated skimmer, leaving the water simmering over the fire. Mash the potatoes and work into them two tablespoonfuls of white sugar and four of flour. Moisten this gradually with the boiling hop tea, keeping the pot on the fire all the time to make sure of the boiling point. When all the tea is in and you have squeezed the hop bag into the last cupful, beat the batter for three minutes and set aside until it is lukewarm (covered). Now add four tablespoonfuls of lively yeast, or a yeast cake dissolved in half a cupful of warm water, and pour into a bowl or wide mouthed crock to “work.” Set in a sheltered corner or in a closet out of draughts until it ceases to bubble.
It will be light in six hours in summer. It may require ten in winter. When it is light and still, bottle.
When you are ready to use it, take the desired quantity out of the jug or jar and return the rest, closely corked, to the cellar or icebox. Half an hour in the hot kitchen may start it to working again or sour it.