You can find this exercise on page 173 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: FLEXIBILITY, HIPS, LEGS - FEET
Begin kneeling on all fours. Bring right knee forward between hands and turn right foot inward toward the outside of the left hand. Slowly slide the left leg back moving it away from the left hand. There should not be any pain in right knee. As flexibility allows, fold forward onto elbows and relax head and neck toward floor. Hold for 10 seconds letting your body relax fully with every exhale.