Position racks in the upper and lower thirds of the oven and preheat to 200 degrees . Line 2 cookie sheets with parchment paper. Using an electric mixer fitted with a whisk, beat the egg whites and salt on medium speed until thick and foamy. Sprinkle in the confectioners' sugar and, once incorporated, beat at high speed until firm and glossy, about 5 minutes.
In a medium bowl, toss together the coconut, rice cereal and cornstarch. Using a rubber spatula, gently fold into the egg mixture until combined.
Drop rounded teaspoons of the mixture about 1 inch apart on the prepared cookie sheets. Bake until firm and dry to the touch, about 1 hour. Let cool completely.