You can find this exercise on page 159 of the book Synergistic Golf.
Exercise Type: HEAVY BALL
Exercise Category: BALANCE, CHEST, POSTURE, POWER PRODUCTION, SHOULDERS, STRENGTH
Assume plank position with ball under right hand and feet placed slightly wider than hips. Perform one pushup. As you straighten back up, push left hand off floor and rotate body toward the left reaching right hand to sky. Try balancing body weight on both feet and right hand on ball. This is an advanced move, which takes much strength and power. Work up to it slowly just slightly lifting hand off floor at a time. Try 5 repetitions then switch sides.