Preheat oven to 250°. Beat the egg whites until they begin to foam. Beat in cream of tartar, salt, and extract. Then, tablespoonful by tablespoonful, add the sugars alternately, beating all the while. This will take time, perhaps some 15 minutes. Just keep on beating until the whites are very stiff. Drop by heaping teaspoonsful onto foil-lined baking sheets. Don't make them too big, or they won't cook properly. And, yes, this will likely make more than you can bake in a residential oven in a single batch, so just keep the extra sheets to the side.
Bake each batch in the center of the oven for an hour. They should be lightly golden, no longer white. When all the batches have finished baking, turn the oven off and return all the sheets to the oven to sit overnight in the cooling oven to dry out.
Peel from the foil the next morning and store in an airtight container.
