Actually, I believe it refers to the 'four main powers' (peng, lu, ji, and) and the four additives powers thereof.
What do you think 8 powers refers to, Graham?
Hi Bob. I see. So in taijigongfu that is what it refers to. O.K. Another thing learned.
In Aikido I use those compass points and we call it eight directions.
In Aikido however and specifically on Ueshiba's statements about it then eight powers is mentioned with relationship to the universe, life living and fundamental to Aikido. This eight powers is of the Kotodama, thus spiritual principles.