The "Caucasian palm" is your hand. Take a reading of the palm with the sun on the palm for a subject in the sun; take a reading of the palm with the shade on the palm for a subject in the shade. But the palm of all skin colors and races does not have skin pigment so it works for everyone. I used that when I was shooting slides on a ski slope because the light meter reading would produce slides that showed the contours of the snow and the mogals, but everthing else would be black or almost black. This gives good results when the lighting is tricky.