"Baking ammonia" was a type of baking powder that can be replaced with a modern double-acting baking powder. Not knowing the precise date of the recipe, it is difficult to know how much baking ammonia or lemon oil could have been purchased for 5 cents; probably about 1 tsp. Of baking powder and 1/2 tsp. Of lemon extract would be appropriate.
Soak the baking ammonia in the milk overnight. The next day, cream the sugar and lard together, then add the beaten eggs, lemon oil, and milk-ammonia mixture; beat until smooth. Mix in enough flour to make the dough stiff enough to roll. Roll the dough out into a sheet about 1/4 inch thick. Cut it into pieces, prick with a fork, and bake until crisp and just starting to change color in a hot oven (about 400°); this should take about 5 to 8 minutes.
