Tip-Top Cake

Dissolve one teaspoonful of soda in one cupful of sweet milk

From 1861:

Dissolve one teaspoonful of soda in one cupful of sweet milk, add one and a half cupfuls of sugar, two eggs well beaten, and one tablespoonful of melted butter, with spice to the taste.
Stir two teaspoonfuls cream of tartar in two and a half cupfuls of floor, then mix the whole and bake it in a quick oven.