Preheat oven to 175°F and line 2 large baking sheets with parchment paper.
Beat whites with salt in a standing electric mixer at high speed (or with a handheld mixer in 2 batches) until they just hold stiff peaks. Gradually add sugar, beating at high speed until whites hold stiff, glossy peaks.
Spoon half of meringue into pastry bag and pipe 1-inch-wide kisses onto 1 baking sheet, about 1/2 inch apart. Pipe more kisses onto second sheet in same manner. (All kisses will fit on 2 baking sheets.)
Bake meringues in upper and lower thirds of oven until crisp but still white, about 2 hours.
Turn off oven and cool meringues in oven 1 hour, then cool completely on sheets on a rack.
8 large egg whites
3/4 teaspoon salt
2 cups superfine granulated sugar