You can find this exercise on page 122 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: FLEXIBILITY, HIPS, LEGS - FEET
Sit tall with bottoms of feet together. Press elbows down lightly on inner thighs to promote stretch. Pull belly button to spine and lean chest forward toward feet for greater stretch. Do not bounce without control. Stretch and focus on breathing for 30 seconds.