In a large saucepan combine the sugar, corn syrup and water and bring to a boil. Continue to boil, undisturbed, until a candy thermometer registers 265 degrees F, or the hard-ball stage. Remove from the heat.
In a standing electric mixer, whip the egg whites and salt until stiff peaks form. Working very slowly, add the syrup in a thin, steady stream, and continue beating on high speed until the candy begins to lose its shine - this can take as long as 10 or 15 minutes, depending on your mixer. (When adding the hot sugar syrup to the egg whites, make sure to stop occasionally to scrape down the sides of the bowl if any syrup has collected. When the beaters are lifted out of the candy mixture, it should fall in a smooth thick ribbon that mounds on itself.
Working quickly, fold in the vanilla and nuts and drop by tablespoonfuls onto waxed paper. Cool completely before serving. The candies will firm up as they cool. Store in an airtight container.