I'm throwing this question out here partly due to the fact that there is no ninjutsu forum and also partly because it is somewhat related to energy cultivation (via tantric yoga/buddhist qigong).

I'm doing some research on the hand mudra(s) that the founder of Aikido can be seen doing here:

So that we all have a common base from which to continue, I'm using this article here as a basis for discussion:

I'm interested to hear how others use these hand mudras for energy cultivation and if there are similarities (and differences) across the board.