Preheat the oven to 250°. In a large bowl, beat the egg whites until soft peaks form. Beat in the brown sugar, 1 tablespoon at a time. Add the salt and beat until the meringue is thick and glossy, about 2 minutes longer.
Spoon 2-inch-wide mounds of the meringue onto 2 parchment-lined baking sheets. Bake in the center of the oven for 1 hour and 10 minutes, or until the meringues are no longer sticky to the touch. Turn off the oven, prop the door open 1 inch and let the meringues cool for 1 hour before serving.