You can find this exercise on page 16 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, FLEXIBILITY, LOW BACK, POSTURE, STRENGTH
Lie on back with legs together extended in the air at an angle while back is imprinted flat on floor. Send legs overhead while spine flexes. Inhale and hold. Exhale and roll down one side of spine with feet over that same shoulder. Once tailbone reaches floor, circle legs around to other side and roll off again on that side. Reverse and repeat 5 time each side.