Quetelet’s statistical researches on the development of the physical and intellectual qualities of man, and an exposition of his concept of the “average man”, which became the by-word of quantitative studies. "Quételet suggested that the ratio of the subject’s weight divided by the square of the height could be used as a measure of fatness that corrected for differences in height. This unit, the Body Mass Index (BMI), is still known as the ‘Quételet Index’ (QI) in some European countries; BMI has been shown to correlate with body fat content, and to predict risk for several of the comorbidities of obesity" (Bray, History of Obesity, IN: Obesity: Science to Practice Edited by Gareth Williams and Gema Frühbeck [2009]). English translation as A treatise on man and the development of his faculties (Edinburgh: William and Robert Chambers, 1842). Digital facsimile of the 1835 edition from the Internet Archive at this link, of the English translation at this link. See No. 171.