You can find this exercise on page 280 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: BACK, FLEXIBILITY, POSTURE, SHOULDERS
Stand with elbows at 90 degrees palms facing up and out to sides of body. Elbows are sticking to ribs. Inhale externally rotating arms outward sticking chest out slightly and shoulder blades slightly squeezing together. Exhale brings arms to crossed position in front of body. Elbows will still stay in tight. Shoulder blades will slightly flare outward imposing a stretch under them. Repeat process 10x alternating crossing hands in front of body.