In whatever field of activity one focuses, an individual gains various forms of knowledge and power of action. This is true in the physical world, with athletic performance, the world of art, music, science, philosophy or business. It is true in terms of inter-relations between people, governmental relations, child-rearing and education. So it should be no surprise that those who focus on gaining an inner psychological mastery through the practice of Raja Yoga will also acquire forms of knowledge and power that are not generally known or accessible to those who do not specialize in this field.
The texts on Raja Yoga, including the seminal work by Patanjali, as well as commentaries such as the famous series of lectures by Swami Vivekananda, describe a number of occult powers, known as Siddhis, that can arise during the practice of Raja Yoga. These powers may include things such as clairvoyance, clairaudience, levitation, traveling out of the body and observing phenomena while having the out of body experience, telepathic powers, and many others that occasionally are exhibited in a non-practicing individual here or there, since these are latent powers of evolving humanity. Of course, they make it clear that these can (and are) distractions from the main goal, but they feel obliged to describe them and advise the student of this science of what may take place as the practice advances.
Sri Aurobindo observes: “These powers and experiences belong, first, to the vital and mental planes above this physical in which we live, and are natural to the soul in the subtle body; as the dependence on the physical body decreases, these abnormal activities become possible and even manifest themselves without being sought for. They can be acquired and fixed by processes which the science gives, and their use then becomes subject to the will; or they can be allowed to develop of themselves and used only when they come, or when the Divine within moves us to use them; or else, even though thus naturally developing and acting, they may be rejected in a single-minded devotion to the one supreme goal of the Yoga. Secondly, there are fuller, greater powers belonging to the supramental planes which are the very powers of the Divine in his spiritual and supramentally ideative being. These cannot be acquired at all securely or integrally by personal effort, but can only come from above, or else can become natural to the man if and when he ascends beyond mind and lives in the spiritual being, power, consciousness and ideation. They then become, not abnormal and laboriously acquired Siddhis, but simply the very nature and method of his action, if he still continues to be active in the world existence.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 28, Rajayoga, pp. 519-520