I'll be interested in the Takeda-China connection you've uncover. I know of at least one that no one seems to mention; that is Jikishinkage-ryu. One of the headmasters in the 17th century lived in Beijing for a decade or more where he taught Shinkage-ryu and studied boxing and spear. Jikishinkage-ryu is fairly unique among the Shinkage-ryu branches in organization and the training methods. Takeda was said to be known as the Aizu no Kotengu *after* his time at the Sakakibara dojo. Maybe it is has something to do with the training?
Sorry for the thread hijack. I do enjoy a few yoga poses such as the various Marici asana. They are all twists that feel good on my back. They are poses dedicated to the warrior goddess Marici, in Japanese Marishiten. one of the more popular warrior goddess who grants devotees invisibility and armor in battle. See Dr. David Hall's PhD dissertation, "Marishiten:Buddhism and the Warrior Goddess" for more information.
I wasn't thinking of that - but Jikishinkage has ties of its own, of course.