What are the classical/canonical books written about Aikido? I am interested in all styles (aikikai, iwama, yoshinkan, shodokan, whatever) training "manuals" as well as more philosophical work.
I am taking the hit, see this meta discussion. Suggestions as to how to make this type of questions on topic are appreciated -- feel free to edit this.
Just because there is an accepted answer does not mean I am not looking for more answers!