From that, the covering to the light of the Chitta is attenuated.
In plain words: Through breath control, the covering over the mind's natural light grows thinner. The mind (Chitta, the mind-stuff) already holds knowledge, but restlessness and dullness hide it.
The Chitta has, by its own nature, all knowledge. It is made of Sattva particles, but is covered by Rajas and Tamas particles, and by Pranayama this covering is removed.
Namaste.
A calm guide to life, the mind and the old teachings.