You can find this exercise on page 308 of the book Synergistic Golf.
Exercise Type: DB STRENGTH
Exercise Category: LEGS - FEET, LOW BACK, POWER PRODUCTION, RHYTHM - TIMING, STRENGTH
In wide stance, hold 3-5-8lb weight in LEFT hand. From impact position, follow through with left hand to balance finish position. Keep right shoulder down and flip right heel over. Repeat 20-30x focusing on balance and posture.