This is an account by a Westerner of the theory and practice of yoga. Bernard studied yoga, going back to the primary texts, and this book is very useful in that it includes copious notes from original sources. He went to India and Tibet and practised yoga under the direction of a guru. He records his experiences in detail, both what he did and what it felt like.
The introduction has a classification of the types of yoga (page 16) which is more detailed and somewhat different from many other sources.
The book includes some excellent photographs of Bernard doing the key asanas. He confirmed that doing the asanas resulted in increased physical fitness and muscle tone, plus a feeling of well-being with the mental results of his good condition.
He describes the six main types of purification: Dhauti (stomach), Basti (colon), Neti (head), Uddiyana (abdominal lift), Nauli (rolling abdomen), and Bhastrika (bellows). He states that their general effect was better health.
Pranayama becomes possible once the channels (nadis) have been cleansed, they are a kind of purification too.
He carried out the mudras that assist in the awakening of Kundalini.
In order to attain samadhi, he spent three months in a retreat under the guidance of a guru. Using fasting, the asanas, purification, pranayama and mudras, and with the candle-gazing technique, he was able to reach a trance-like state and see the light associated with samadhi.