You can find this exercise on page 273 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: ARMS - HANDS, CLUB CONTROL - ACCURACY, FLEXIBILITY
Kneel on all fours with knees and hands body width apart. Press the back of the hands to the floor spreading the fingers wide. The palms will be up and fingers pointing toward knees. Hold four five seconds then release. Repeat 3 times. Do not force stretch or put too much weight into hands.