The pranayama, breathing exercises, we do are described in the old hatha yoga texts, primarily the Hatha Yoga Pradipika by Swatmarama from the 13th century.

We have learnt these from Sri O. P. Tiwari, a sanskrit scholar, advisor to the Indian government on yoga, and head of the  Kaivalyadhama Yoga Institute, founded by his teacher Swami Kuvalayananda.

The purpose of the pranayama practices is to directly access the energies that control all body and mind functions, and to strengthen, balance and deepen them. The effects are increased physical well being, mental calm, and emotional strength and balance.

We use various meditation techniques or pratyahara, dharana och dhayanaas they are called, from various yogic and Buddhist traditions, but mainly the techniques taught by Paramahansa Yogananda. 

Pratyahara is the fifth branch of Patanjalis ashtanga yoga, where we focus our awareness inward, away from sensory input, and from the part of the mind that processes these inputs. Dharana is the sixth branch, where we intensify our focus, until the focus, that which is focused upon, and that which is aware of the focus become one. We then reach the seventh branch, dhayana, a calm meditative state of mind filled with compassion, wisdom, intelligence, and strength.

Through dhayana we can then reach samadhi, the final branch, and the goal of all yoga, where we gain insight into our true, immortal nature.