Lovely saying...and it is not my own. It's from a Chinese grandmaster who taught in Japan for 11 years. Including two of Sagawa's students.
Many people in Japan talked to me about Ki.
When asked "Where is yin? Where is yang?
So where then, is this Ai-ki?
You cannot pretend Dantian
You will be found out.
The quandary for most is that
You cannot be soft
Without being strong
How can this be?
How is it done?
I say the answer lies in
"Aiki in me, before aiki between thee and me."
Ueshiba knew that and cited that...Heaven/earth/man...released the mountain echo.
A body so tough and resilient that the opponent...bounced...or echoed off.
He was famous for it?
For those taking part in his lineage....
How did he do it?
What did he mean?
Why does it have immeasurable value in producing aiki?
I would say yin and yang come from one point. They are one, inside and outside.
Anything in me exists before between me and thee so obviously that would apply to Aiki or anything else so I fail to see any other significance to the statement if there is any.
Don't know what the significance of bouncing off is apart from a skill based on stillness. Hardly all embracing Ai ki as I see it. Part of maybe but wholly? No, not to me.
Valuable? Yes. Limited as far as Aikido potential? Depends solely on your intention and purpose.