Densho (伝書)
Densho (books on the esoterica - also written as 傳書) is a manuscript or book of secret techniques of schools of Japanese art and martial arts.
It could be called a type of textbook or a manual nowadays, but was not written for beginners or for general public. It is a manuscript that included the structure of that school, oral lesson, methods, or secret techniques that granted to an heir or the one who received mokuroku (a certificate of the completion of the art) or a permit from the master. There is also the Shito-ryu school of Karate School that renew densho and pass it down.
Main Densho
Fushikaden (The Flowering Spirit)
Go Rin no Sho (A Book of Five Rings)
Chakyo (Chaijing or The Classic of Tea)