A natural position -
"Never paint a picture as if the person was laying. A natural position can be maintained for a few seconds, it's like a flash. You just put down some great brands for the selected position of the head, hands, feet, etc., and keep the assembly of the sitter in them. "
Quote Charles Lasar, Tips for Art Students (Duffield & Company, New York 1923
Drawing by John Singer Sargent.