1. In heavy saucepan over medium heat, stir together sugar, corn syrup and the cold water just until sugar is dissolved; do not stir after this point. Cook mixture until it registers 260 degrees F on candy thermometer (hard ball stage).
2. Meanwhile, in large clean bowl of standing mixer, beat egg whites until stiff peaks form. On high speed, carefully pour steady stream of hot syrup mixture into beaten whites. Add vanilla; continue to beat until mixture holds its shape, about 7 to 10 minutes. Stir in chopped pecans.
3. Using 2 spoons, drop divinity onto waxed paper, using 1 spoon to push candy off the other. This may take practicethe technique is to twirl the pushing spoon, making candy top finish with a swirl. You may also wish to transfer divinity to a piping bag with no tip, and pipe mounds onto waxed paper. If mixture does become too stiff, add a few drops hot water. Store divinity at room temperature for up to 1 week.