The ancient yogis discovered

that the secret of cosmic consciousness is intimately linked with
breath mastery. This is India’s unique and deathless contribution to the world’s treasury of knowledge. The life force, which is ordinarily absorbed in maintaining the heart-pump, must be freed for higher activities by a method of calming and stilling the ceaseless demands of the breath.
— Swami Sri Yukteswar


For those interested, here is an abbreviated version for better meditation and mastery of breath (The Hong-Sau Technique of Concentration). This technique has been practiced by students of Yoga for millenia.

Breath, the life force Prana!

Sit upright with a straight spine, and relax your body (Your spine must be straight, and you must be able to relax completely).

With your eyes closed, look at the point midway between the eyebrows on your forehead. Inhale slowly, counting to eight. Hold the breath for the same eight counts while concentrating your attention at the point between the eyebrows.  Exhale slowly to the same count of eight.

Repeat three to six times.

End your practice of the technique by taking a deep breath, and exhaling three times. Then, keeping your mind focused, and your energy completely internalized, try to feel peace. Sit for at least five minutes enjoying your deeply relaxed state.
A key point is to maintain the symmetryin each of the segments. After inhaling and exhaling completely, wait for the next breath to come in. When it does, mentally say Hong (rhymes with song). Then, as you exhale, mentally say Sau (rhymes with saw). Hong Sauis a mantra (Sanksrit term). It means ‘I am He’ or ‘I am Spirit’.
At no time during the practice of this technique should you make any effort to control the breath. Let it flow naturally. Gradually, you may notice that the pauses between the inhalation and exhalation are becoming longer.
Enjoy these pauses, for they are a glimpse of the deep peace attained in advanced meditation.
In modern times, in 1861, an elusive and mysterious master, Mahavatar Babaji, re-introduced the ancient Kriya technique to the general public through his able disciple, Lahiri Mahasaya. He had many realized disciples.
Foremost among them were Swami Sri Yukteshwar Giri, who was well versed in the scriptures of both the East and West, and who attained the highest state of realization. Among the many disciples of Swami Sri Yukteswar were Paramahamsa Yogananda, author of Autobiography of a Yogi.
Kriya, controlling the mind directly through the life force, is the easiest, most effective, and most scientific avenue of approach to the Infinite. In contrast to the slow, uncertain “bullock cart” theological path to God, Kriya may justly be called the “airplane” route.

Paramhansa Yogananda