Introduction: The term Yoga, used here, refers to the Yoga System. Thus, this writing does not pertain to any of types or schools of so-called "yoga" prevalent today. Whilst these tend to use some aspects of the Yoga System, they neither posess its positive effects nor its benefits.
The knowledge of Yoga could perhaps be compared to a river. A river begins its journey from pure and clean water sources in the mountains. Whilst we can find the clearest water at the beginning of the river, this water can often become muddy and contaminated as it flows downward and reaches the ocean. By no means can water taken from the foot of a river show how clean and clear it actually was at its source. Therefore, if we try to determine its quality at the place where the river reaches the ocean, we would inevitably come to the wrong conclusions. If we want to understand the essence and particularities of the water we need to examine the river at its source.
Yoga serves humanity for better health and spiritual evolution.