Make a Lump of Dough, about two Pounds of your last making, which has been raised by Barm, keep it by you in a wooden Vessel, and cover it well with Flour. This is your Leaven; then the Night before you intend to bake, put the said Leaven to a Peck of Flour, and work them well together with warm Water. Let it lye in a dry wooden Vessel, well covered with a Linnen Cloth and a Blanket, and keep it in a warm Place. This Dough kept warm will rise against next Morning, and will be sufficient to mix with two or three Bushels of Flour, being worked up with warm Water and a little Salt. When it is well worked up, and thoroughly mixed with all the Flour, let it be well covered with the Linen and Blanket, until you find it rise; then knead it well, and work it up into Bricks, or Loaves, making the Loaves broad, and not so thick and high as is frequently done, by which means the Bread will be better baked: Then bake your Bread.
Always keep by you two or more Pounds of the Dough of your last baking, well cover’d with Flour to make Leaven to serve from one baking Day to another; the more Leaven is put to the Flour the lighter and spongier the Bread will be, the fresher the Leaven, the Bread will be less four.
From the Dublin Society.