You can find this exercise on page 26 of the book Synergistic Golf.
Exercise Type: HEAVY BALL
Exercise Category: POWER PRODUCTION, RHYTHM - TIMING, STRENGTH
Stand with your body in address position holding a heavy ball in both hands instead of a club. Perform a slow smooth controlled takeaway and downswing. Remember to keep head still throughout movement and maintain normal swing angle. Focus on rotating shoulders away from target with minimal hip rotation. Repeat 10 times one side then switch to opposite handed backswing to promote symmetry.