Combine sugar, salt, vanilla, milk, and eggs. Stir well; strain. Put 1 tablespoon caramel sauce in each of four or five 6-ounce custard cups, or put 4 tablespoons sauce in a deep 1-quart baking dish. Pour custard carefully over caramel sauce. Place cups or baking dish in a pan about 2 to 21/2 inches deep; pour boiling water around cups to come almost to level of custard. Bake 30 to 40 minutes, or until a knife inserted near center of custard comes out clean. Remove custard cups or baking dish from water at once. Chill thoroughly before unmolding. (Custard may be served warm, if you prefer, but it won't unmold unless it is chilled thoroughly.) Custard may be baked without sauce, if preferred, with a sprinkle of nutmeg on top. For a glamorous buffet-supper dessert, bake caramel custard in a ring mold; unmold on a plate to fit the ring, and fill the center of the ring with whipped cream. Increase recipe to fit the size of mold used (for a 6-cup mold, this recipe should be doubled).