It might be clearer if you remember this passage from the first Floating Bridge of Heaven
It is said that Aikido is "Standing on the Floating Bridge of Heaven". The Floating Bridge of Heaven is the turning of fire and water bound together. Fire moves water, water is moved by fire. Fire and water are one thing. They turn in a spiral. They are entwined through Ki. That is something that is enacted through the breath ("iki"). This breath ("iki") is Aiki.
I have been worried, though, by the idea that yin is on the left and yang is on the right and I was wondering about methods of combining them. I thought of O Sensei doing furitama, or "soul-shaking," where you hold the hands together at the hara and lightly bounce up and down. And I thought that's what he's doing there, balancing yin and yang in the two hands and spreading the energy through his body.
So I went looking for examples of furitama and found this article, which reads exactly right, but only if you understand the precise meanings of some gloss-over phrases:
Furitama is practiced standing with the legs shoulder-width apart. The hands are placed together with the left hand over the right. A small space is left between the hands. The hands are placed in front of the abdomen and shaken vigorously up and down. Inhale to the top of the head rising up naturally. Then exhale to the bottom of your feet as you continue shaking your hands up and down. The exercise if finished in silent and still meditative kishin.
This chinkon exercise was intended to gather the spirits of the divine into ones center (added emphasis DO)
... calming the spirit... vibrating the soul. It's an effective way to gather your thoughts, center your mind and focus your intention.
END OF QUOTE
This is the kind of statement that is easy for the mind to skip right off of and simply provide a meaning based on the image of "the spirits of the divine." And that, clearly is where so many people have gone tangent to the actual art.
Not only does it not say which spirits, given as plural. It doesn't say how many spirits. And since we know that Japan has kami all over the place, we might think it means "all the gods of Japan," as I think it's actually phrased in the story of Morihei at the well after surviving the Naval officer's sword attacks. There was a purple cloud and all the gods of Japan entered his body...I think.
But if we look at furitama as gathering the specific "spirits" of in and yo into our body and vibrating them along with the body and breath, then it really means aligning the body with the "principles" of in and yo to harmonize and energize it.
So suddenly that exercise looks like it has a lot more meaning than I ever imagined and I'm adding it to my research right away.