Information comes into my head from every direction and lodges there disassociated from its original source. That's troubling because I like to supply the attribution when I offer a factoid. The Internet helps sometimes. Tap, tap, tap, in goes the general idea and out pops the author and the exact quote. Sometimes. Sometimes not.
Haven't looked this one up yet, but it's from someone associated with Downton Abbey and the gist of it is that people sat up straight in those days [turn of the last century English ladies and gentelment, that is] and dining chairs had backs not so you could slouch, but so the servants had something to hold onto when they pulled your chair out for you.