Preheat the oven to 200°. Line 2 large baking sheets with parchment paper. In a metal or glass bowl, using an electric mixer, beat the egg whites with the salt at low speed until frothy. Increase the speed to high and beat until the whites hold firm peaks. Beat in the granulated sugar, 1 tablespoon at a time, until the whites are stiff and glossy, 5 to 6 minutes.
Spoon or pipe tablespoon-size mounds of the meringue onto the prepared baking sheets, spacing them 2 inches apart. Bake for about 3 hours; the meringues should be quite pale and should be dry and crisp throughout. Let them cool overnight in the turned-off oven.