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The Soham (or Soo Hum) mantra...

Soham is a Sanskrit word meaning I myself, although it is often taken to mean It is I or He is I.

When used for meditation, Soham acts as a natural mantra. Because it's based on the sound of your breathing, it helps to control your breathing pattern and aid concentration.

• Sooooo... is the sound of inhalation, and is remembered in the mind along with that inhalation.
  
  
• Hummmm... is the sound of exhalation, and is remembered in the mind along with that exhalation.

Its use as a mantra emerges in mystical Sanskrit literature of the medieval period.

The mantra is sometimes claimed to originate from verse 16 of the Isha Upanishad, which ends:

"Yat te rūpam kalyānatamam tat te paśyāmi yo 'sāv (asau purusah) so'ham asmi."

Which translates as: "The light which is thy fairest form, I see it. I am what He is." (He referring to the person in the sun.)

The Soham mantra is often called the Universal or Natural mantra, because of the fact that it's the sound of the breath - and everybody breathes.