1. Place the egg whites in the bowl of an electric mixer, and beat on high until foamy. Add the cream of tartar and salt, and continue beating until soft peaks form. Still beating, slowly add first the sugar, and then the vanilla extract. Remove the beaters and fold in the cereal.
2. Line a large baking sheet with aluminum foil. (Do not grease the sheet or coat it with cooking spray.) Drop heaping teaspoonfuls of the meringue onto the baking sheet, placing them 1 1/2 inches apart.
3. Bake at 250°F for 45 to 50 minutes, or until firm and creamy white. Turn the oven off, and let the meringues cool in the oven for at least 2 hours with the door closed. Remove the pans from the oven and peel the meringues from the foil.