Ninja warriors were the assassins and espionage experts of feudal Japan. The ninja are often associated with a type of energy meditation known as "kuji kiri" or the nine hand seals, which are derived from the esoteric Buddhist traditions of Shingon and Mikkyo. These hand symbols are still used today by practitioners of ninjutsu, the martial arts of the ninja.
The oldest martial arts of Japan often involve the use of meditations and concepts drawn from the esoteric schools of Japanese Buddhism, such as the Shingon tradition. These sects are considered esoteric or occult because their meditation practices, unlike those found in Zen Buddhism, make use of magic rituals intended to alter reality on some level. This is often interpreted as actual spell-casting, which is one reason people associate it with the mysterious ninja. However, like all schools of Buddhism, the real concern of the esoteric sects is the spiritual enlightenment of the practitioner, and the so-called spells are intended to purify and focus the mind of the person using them.
The kuji kiri or "nine hand seals" are symbolic gestures made by crossing the fingers over each other in certain patterns. The hand seals look mysterious, but they are fundamentally methods of meditation. Each hand seal is associated with a particular quality of psychological and spiritual energy, which can be invoked by the ninjutsu practitioner when he needs that quality for a specific task. For instance, the hand symbol of "sha," which looks somewhat like two hands clasped together in prayer, is supposed to invoke the energy of healing.
How the Seals Work
The kuji kiri hand symbols are meaningless on their own. Simply clasping your hands in a certain way will not produce any powerful effect. What the hand symbols really do is to serve as keys to the practitioner's own memory and mental focus. In other words, the ninja would make a particular hand symbol only to remind himself to access an entire set of associated ideas and concepts stored in the memory. The goal was to enter a certain mindset, which was thought of as a process of opening "energy centers" in the mind and body. This was supposed to give the ninja the spiritual and psychological tools to accomplish the task at hand.
Learning Kuji Kiri Meditation
As in all other forms of Buddhism, the sects that created the nine hand seals were primarily concerned with enlightenment, not victory in war. However, the samurai and ninja both made use of these meditative techniques in order to harness the untapped energies of the mind for success in battle. The nine symbols differ somewhat from one sect to another, but the most widely available way to study them is through a school offering classes in traditional ninjutsu. To study the nine hand seals in more depth, it would be necessary to seek out instruction in esoteric Buddhism from a qualified spiritual teacher.