You can find this exercise on page 100 of the book Synergistic Golf.
Exercise Type: DYNAMIC STRETCH
Exercise Category: ABDOMINALS, BALANCE, FLEXIBILITY, HIPS, LEGS - FEET, LOW BACK, RHYTHM - TIMING
Stand with feet slightly wider than hip distance apart and arms out to sides with elbows bent upward. Shift weight to right foot. Simultaneously rotate right elbow across body as left knee lifts. Elbow and knee may or may not touch. Do not change posture and take elbow down to knee. Shift and repeat other side exhaling on rotation and lift. Repeat 10x alternating.