In a mixer bowl beat together the egg whites, vanilla, salt, and cream of tarter until soft peaks form. Gradually add sugar and beat to stiff peaks and until sugar is dissolved. Fold in chopped pecans. Spread mixture onto bottom and sides of a well-buttered 9-inch pie plate, building up the sides with a spoon to form a shell. Bake in a 300 degree F oven for 45 minutes. Turn off heat and let dry in oven with door closed for 1 hour more. Cool thoroughly on rack. Makes 1 pie shell (8 servings).