Anyone interested in sitting posture and chair design should read "The Chair: Rethinking Culture, Body, and Design" by Galen Cranz.

It's a fascinating analysis of how chairs impact posture and the related biomechanics. It shows why oft-touted "lumbar support" does more harm than good, how attitudes to chairs and posture are affected by cultural expectations, and why there is no perfect chair, but with recommendations for how different chairs manage different tradeoffs -- she ultimately most highly recommends high stools which allow the body to maintain a 135° angle with full foot support -- which the saddle chair accomplishes.

[1] https://www.amazon.com/Chair-Rethinking-Culture-Body-Design/...

A definitive work on this subject that started the trend:

http://www.amazon.com/Chair-Rethinking-Culture-Body-Design/d...

It is also worth noting that Humans were not meant to stand for 8-12 hours a day non-stop either.