Below is an excellent and concise article on the history of both the Northern and Southern branches of Wu Style Taiji Quan. It was written by Tina Zhang who is a student of Li Bingci, (who was a student of Yang Yuting). She and her husband, Frank Allen, live and study in NYC.
Yan Yuting was a student of Wang Maozhai and the teacher of my teacher’s teacher, Wang Peisheng. This is a book I obviously cannot read, but which, nonetheless, has some photographs of Grandmaster Yang doing many of the postures. Even in a still photograph it is easy to see that the alignments are perfect.