Yantra Yoga is a form of yoga characterized by an emphasis on a complex system of mathematics and geometry, which assigns value to the forces that make up the universe.

Yantra Yoga comes from the Tibetan Buddhist tradition and is similar to both Hatha Yoga and Chi Gung. It can best be described as ancient movements and postures, breathing exercises, mudras, and meditation techniques that combine to circulate and rejuvenate the body's energy; it is said that this form of Yoga opens up the inner eye, the sixth Chakra: Ajna.

To eliminate negativity, purify karma, and generate inner peace.

This form of yoga originated in the 8th century CE and taught by Tibetan Buddhist Vairocana. It is considered one of the lesser known forms of Yoga.

Yantra Yoga training teaches Tibetan meditation techniques, prostrations and mantras for karma purification, elimination of negativity, and generating inner peace. The practice of Yantra Yoga includes use of body, speech and mind: the positions and movements work the body, the breathing practices and chanting use the voice, and the visualizations and meditations engage the mind. The result is a holistic and meditative exercise.

Ajna - the sixth primary Chakra positioned at the eyebrows and translates to "command"

Mudras - a symbolic or ritual gesture common in Hinduism and Buddhism

http://www.chakrayoga.com/chakras/yantrayoga.html
http://www.lamalobsang.com/TibetanYantraYoga.htm