This composition of exercises is not to be construed as representative of historical ninjutsu, but rather is informed by ninjutsu principles and concepts considered to be of use in cultivating preparedness skills and ‘neo-ninjutsu’ practices.
Materials that influenced these exercises include:
- The Bansenshukai (1676)
- The Gunpo Joyoshu (1560?)
- The Shoninki (1681)
For a better explanation of the distinction between In-nin and Yo-nin, see: In Praise of Spies by Stephen Nojiri (2012)
I want to draw attention to the importance of tree-climbing and using a tree as a surveillance post in accord with historical ninjutsu.
As noted by Hattori Hanzo in the Gunpo Jiyoshu, shinobi were apt to hide in large trees to listen in or visually observe a locality for information considered vital to their mission. Even today, this technique of hiding in a tree may be considered useful for surveillance purposes or just simple concealment. For a good visualization of how this works, view the following two videos by Stealth Technique: