Re: Need some help choosing some more books?
The big problem is that Morihei Ueshiba did not write anything himself and there is some doubt that he even "taught" at least in the way that word is commonly used.
I see now that "Secret Teachings" is a translation of Aikido Shinzui which, I believe, is a collection of articles from Honbu Dojo's newspaper. I personally do not know how they were written, maybe John Stevens comments on this in the book?
I do know that a book called Takemusu Aiki was dictated by O'Sensei and then checked by him personally. It may be more accurate. A translation is on the aikidoonline web site.
The breathing/meditation is even more problematic. Many teachers teach various systems, but (at least in my opinion) no one can clearly trace them back directly to the founder. Okumura Sensei remarked that O'sensei was very open to students finding and using systems from other sources. O'sensei's way seems to have been kept private with him.
Morihei Ueshiba learned meditation from Onisaburo Deguchi of the Omoto Kyo and it is likely what he learned was at least a part of what he practiced daily for the rest of his life. However, at some point, Omoto Kyo had a problem with people killing themselves after practicing this meditation and suspended teaching it. Perhaps this was part of O'Sensei's reasoning behind not clearly teaching it, I don't know.