You can find this exercise on page 81 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, STRENGTH
Lie on back with legs extended to sky, toes pointed and hands at sides. Inhale to prepare. Exhale articulating spine off floor slowly from tail bone to upper back....not neck. Abdominals will tighten throughout movement engaging and pulling the hips against gravity. Allow legs to lower over head and ideally touching mat. Inhale lift legs to parallel. Exhale sequentially rolling spine back down to mat from upper ribcage to tailbone. Complete 10 repetitions focusing on flat abdominals.