Attitudes of the Head (1886), from Delsarte System of Dramatic Expression.
Source: University of Toronto Libraries / Internet Archive
Available to buy as a print.
https://pdimagearchive.org/images/8892660b-866d-44f9-9101-2d10bffdd0cd

"Sit up straight" is the advice almost everyone's heard.
Researchers measured actual nerve compression across different sitting positions. Upright came out worse than slouching.