Pound Cake Waffles

I'm planning on making these this weekend. From a 1918 edition of The Rumford Complete Cookbook by Lily Haxworth Wallace

Pound Cake Waffles

3/4 c butter (or sub)
1 c fine granulated sugar
4 eggs, separated
1/4 cup milk
1 1/4 c sugar
2 level teaspoons Rumford Baking powder
1/2 level teaspoon salt
1 teaspoon lemon or vanilla flavoring

Beat the butter and sugar to a cream; add the well-beaten yolks of the eggs, milk and then the flour, salt and baking powder sifted together. Put in the flavoring and beat the batter thoroughly. At the last moment foldin lightly the whites of the eggs beaten to a stiff froth, and cook as ordinary waffles.