From 1899:

This recipe is the same as was originally used in General Washington’s family. In those days it was baked in a bricked oven, but it is a fine Christmas cake. One and a half pounds of sugar, half a pound of butter, one and three-fourths pounds of flour, six eggs, one pint of sour cream, one teaspoonful of soda, in the cream; one pound of raisins, one pound of currants, half a pound of citron, one nutmeg, grated rind of two lemons, and a little mace. Cream the butter and sugar together, add the yolks of eggs well beaten, then the cream and flour alternately, then the whites of the eggs well beaten; last of all add the fruit, floured. Bake two hours, covering with a buttered paper, and line the pans with three thicknesses of paper.