Here is a quote that I took from a website on posture photos.
'the pictures were actually made for anthropological research: "The reigning school of the time, presided over by E. A. Hooton of Harvard and W. H. Sheldon" - who directed an institute for physique studies at Columbia University - "held that a person's body, measured and analyzed, could tell much about intelligence, temperament, moral worth and probable future achievement. The inspiration came from the founder of social Darwinism, Francis Galton, who proposed such a photo archive for the British population."
While the popular conception of Sheldonism has it that he divided human beings into three types - skinny, nervous "ectomorphs"; fat and jolly "endomorphs"; confident, buffed "mesomorphs" - what he actually did was somewhat more complex. He believed that every individual harbored within him different degrees of each of the three character components. By using body measurements and ratios derived from nude photographs, Sheldon believed he could assign every individual a three-digit number representing the three components, components that Sheldon believed were inborn - genetic - and remained unwavering determinants of character regardless of transitory weight change. In other words, physique equals destiny.
It was the pop-psych flavor of the month for a while; Cosmopolitan magazines published quizzes about how to understand your husband on the basis of somatotype. Ecto-, meso- and endomorphic have entered the language, although few scientists these days give credence to Sheldon's claims. "Half the textbooks in [his] area fail to take [him] seriously," remarked one academician in a 1992 paper on Sheldon's legacy. Others, like Hans Eysenck, the British psychologist, have suggested that Sheldon wasn't really doing science at all, that he was just winging it, that there was "little theoretical foundation for the observed findings."
These photos were also perhaps an off-shoot of various types of anthropological photos that were very popular at the beginning of the 20th century, in which it was customary to compare body types and physique of the many native ethnic groups then under colonial rule by European nations. Anthropologists would make detailed naked photos of all kinds of people, order them into some kind of hierarchy which invariably ended up with north Europeans leading the bunch.
These photos might also be accompanied by line drawings of the same naked subjects and bodily proportions and sizes were described or detailed into making some kind of physiological point.
Such books of anthropological photos and 'studies' were quite popular and sold very well, to professionals such as doctors, lawyers, notaries and such.
Taking posture photos of American college students is a sort of off-shoot of this type of study. But where previously ethnic types were the distinguishing factor about which comparisons were made on a general scale, the posture photos studies were meant to study the differences between body types within an ethnic group within one nation, to see if any generalizing statements could be made as to intelligence, achievements or moral character depending upon body types.
Here are a few examples of both photos and drawings
http://www.zity.biz/index.php?mx=album;ox=showcat;done;c=4156