This makes a large cake.

From 1913:

One cup of butter, two cups of sugar, four eggs, half a cupful of sour milk in which dissolve half a teaspoonful of soda, two cups of flour, one cupful of grated raw potatoes, two ounces of chocolate, cinnamon, nutmeg, and cloves to taste, say about half a teaspoonful of each.
Bake in loaves or in layers.
This makes a large cake. For our family I usually take half the quantity of ingredients. This makes a nice sized cake for us.
Mrs. O. C. H.