The principles of phrenology
An 1838 Edinburgh and London treatise on phrenology by Sidney Smith, aimed at students of the pseudoscience that read character from the skull's shape. The four profile drawings show bald or balding heads in side view with numbered lines marking cranial zones, with the ear and jaw set against the outline of the skull. A designer could take the clean single-line profile style and the diagrammatic measurement annotations as a model for scientific schematic figures.
