Trataka is gazing and is a traditional meditation practice of Yoga and Tantra. So Ham (or So Hum) is a Universal Mantra, as it relates to the breath, and everybody breaths. So Ham is a Sanskrit word that means I am that, or I am that I am.
Inhale with the sound So, and exhale with the sound Hum. Allow the sounds to silently repeat in your mind, without speaking them aloud. There are a total of 40 So Hum and breath repetitions The speed of one repetition is 9 seconds per breath, which is 6 2/3 breaths per minute. This rate is ideal for relaxing the autonomic nervous system, and also preparing for deep meditation. Breathe with your diaphragm, while gazing at the center, silently remembering So with inhalation and Hum with exhalation.