The study of body language is a relatively modern field - indeed you only have to look back as far as the latter part of the 20th Century to locate when interest in the topic - both academically, and among the general public - really began to take off.
However, in the history of body language there are pioneers whose interest in the topic can be traced back much earlier.
Francis Bacon was an English philosopher, politician and scientist. Writing in Of the Proficience and Advancement of Learning, Divine and Human - first published in 1605 - Bacon had the following to say about gestures of the body when discussing the concept of knowledge of ourselves.
Aristotle hath very ingeniously and diligently handled the factures of the body, but not the gestures of the body, which are no less comprehensible by art, and of greater use and advantage. For the lineaments of the body do disclose the disposition and inclination of the mind in general; but the motions of the countenance and parts do not only so, but do further disclose the present humour and state of the mind and will.
For as your majesty saith most aptly and elegantly, “As the tongue speaketh to the ear so the gesture speaketh to the eye.” And, therefore, a number of subtle persons, whose eyes do dwell upon the faces and fashions of men, do well know the advantage of this observation, as being most part of their ability; neither can it be denied, but that it is a great discovery of dissimulations, and a great direction in business.
The King of Body Language
Not only is Francis Bacon arguably the first person to consider body language from an empirical persepctive but he also identified the world's first body language expert - King James the First.
For as your majesty saith most aptly and elegantly, “As the tongue speaketh to the ear so the gesture speaketh to the eye.”
Francis Bacon - we salute you!