Sift two cupfuls of flour with a pinch of salt and two teaspoonfuls of baking-powder. Work into it a tablespoonful of butter, add the yolk of an egg beaten with half a cupful of sugar, and one cupful of milk. Fold in the stiffly beaten white of the egg and add a heaping cupful of blueberries, which have been dredged with flour. Bake for half an hour in muffin pans. Sour milk may be used with half a teaspoonful of soda instead of the baking powder.
The Myrtle Reed Cook Book, 1916