You can find this exercise on page 94 of the book Synergistic Golf.
Exercise Type: TOWEL
Exercise Category: FLEXIBILITY, LOW BACK, RHYTHM - TIMING
Stand tall with feet slightly wider than hip width and ends of towel in hands with arms extended out chest high. Inhale to prepare. Exhale rotating and pulling towel with right hand to the right. Keep rotating allowing left heel to lift for maximal rotation behind you. Inhale back to center and repeat other side. Alternate focusing on lifting spine higher and higher each time. Repeat 10x.