You can find this exercise on page 89 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: BALANCE, FLEXIBILITY, HIPS, LEGS - FEET, LOW BACK, POSTURE
Starting from triangle pose with right foot forward and left arm in air, slowly bring left arm down to where right arm is. Rotate body and take right arm in the air with upper body facing opposite direction from first triangle. Focus will be placed on pulling belly button in to help enhance rotation and opening chest. Hold approximately 10 seconds and switch sides.