One of my favorite books is by Marianne Wex. She photographed men's and women's body language and posture. She wrote about the differences between them as well as posed them in reversed poses (men doing feminine postures and vice versa). In many ways it is a very 70s type of feminist book, but for me it is also a book that grants importance to human physicality in a way that's more intellectual than I'd ever encountered before.
The book is called Let's Take Back Our Space: on "Female" and "Male" Body Language and I can find very little information about it online. I've found a bunch articles that reference the work that are good, but don't really talk about it in the way I've found it interesting (in terms of thinking about clothing). Here are a few good links in English (there are loads more in German):
Dr. Allen Farber
This one's a bit of a mystery, you have to click through an agreement form....
I believe this is the biblio info from the book I used at the CSM libraries:
Wex, Marianne (1979): ‘Let’s Take Back Our Space’: "Female" and "Male" Body Language as a Result of Patriarchal Structures (trans. Johanna Albert). Berlin: Frauenliteraturverlag Hermine Fees
I didn't write down any of this information myself so I'm not really sure this is correct, but as far as I can tell this is her only book. The pictures on this page are all scans from my photocopies and unfortunately the only pictorial evidence I could find of the Wex's work online or off. If anyone has more information about Marianne Wex and her work I'd love to hear about it!
Woman and man in masculine poses
Woman and man in feminine poses
Woman in masculine poses
Man and two women in feminine poses