You can find this exercise on page 77 of the book Synergistic Golf.
Exercise Type: STRENGTH
Exercise Category: CLUB CONTROL - ACCURACY, POSTURE, RHYTHM - TIMING, SHOULDERS, STRENGTH
In address, hold 3-5-8lb dumbbell in right hand and cross forearm over stomach. Swing weight up and back into top position. Repeat 20-30x focusing on posture and core strength.