In a 2-quart saucepan, combine sugar, corn syrup, salt, and water. Cook to hard-ball stage (260 degrees F, or 125 degrees C), stirring only until sugar dissolves.
Meanwhile, beat egg whites to stiff peaks. Gradually pour syrup over egg whites, beating at high speed on electric mixer. Add vanilla and beat until candy holds its shape, about 4-5 minutes. Quickly drop from a teaspoon onto wax paper; cool.