Although believed to be a Ninja secret the Kuji~In was also used by the Samurai. Where it came from no one is sure but it does have similarities to Hindu and Tibetan Mundras. The Kuji~In is more a way of concentrating the mind than weaving magic with ones hands despite many Sensei and movie companies attempts to prove otherwise.

I personally have practiced this for several years. Though I admit I have gotten rather lazy about it lately. Following are links to each individual meditation, and a brief summary of how i feel each one works. I also may add that it is believed that saying all nine consecutively and doing the had gestures for each removes curses. Enjoy!