Telepathy is a greek word which is made of two terms ‘tele’ means “distant” and pathy/patheia meaning “to be affected by”, is supposed to be the transfer of information on thoughts or feelings between individuals by means other than the five senses. This is a communication through means other than the senses, as by the exercise of an occult power.
It has been used since yore by the mystics in some ways. This can be used by the ones who are spiritually developed and who practice concentration development exercises, the self introspection, meditation and Samadhis.
It is mentioned in Puranas (which is considered by Chhandogya Upanishad as 5th Veda), that the highly elevated souls would know and understand the thoughts, emotions, desires of the people, who are called as Antaryamin. This issue (Antaryamin) is explained in detail in the seventh Brahman of 3rd chapter of Brihadaranyak Upanishad (which is the greates Upanishad amongst all). Sage Yajnavalkya, the leading Seer of this Upanishad, discloses this mystery unto the son of sage Arun named Uddalak. When you go through the revelations, meditate on them and understand you know and realize that the very Soul of all the beings is all knowing one (Antaryamin). Whosoever understands this mystery, believes strongly and becomes convicted, becomes Antaryamin. Our Soul is All Knowing One, so long we live merged with That, we are All Knowing One, we can hear distant talks, chatterings (Door-shravan); we can have remote viewing (door darshan), and some other psycich perfections. We can develop our ESP (Extra Sensory Perception) and can enjoy some or all of siddhis. Apart from it, knowingly or unknowingly every body, even ignorant of all these mysteries, can receive or send the thoughts.
Rigveda tells that our thoughts have 4 layers – 1. Para (Subtlest layer, which is the fastest communication, you think and that is prompted in no time), 2. Pashyanti (3rd layer, which is used by angels or devas/devis, this that plane of thoughts where Telepathy takes place), 3. Madhyama (2nd layer, which is expressed and understood by gestures) and 4. Vaikhari (the gross layer of thoughts, which are spoken or written and can be undertood even by layones). The three inner layers of thoughts are used by all and understood by the Seers or Yogis only but the gross most layer named vaikhari is used and understood by almost all except the lunatics.
It is said that once Maharishi Raman had received a telepathy of an aspirant who was roaming somewhere in Delhi in the search of a True Guru, he inspired him from there and that aspirant reached to his Ashram.
Telepathy is one of Super Natural Powers (Siddhis) which can be developed with some of the practices of Ashtanga Yoga of Sage Patanjali such as – concentration (dharana), meditation (dhyana) and trance (samadhi). Patanjali’s Yoga Sutras, the classic text on Yoga, lists several exercises which accelerate the development of eight Siddhis ranging from invisibility to walking on water. In Yoga or Spirituality siddhis are believed as side effects of the meditation and suggested not to heed them, even by some of sages they are forbidden. The visions of gods may appear and occasionally supernatural powers such as clairvoyance and telepathy are developed. Both of these effects can be deliberately produced. Concentration on a mental image will sometimes result in visions, particularly if the concentration is done with devotion or if there is a strong desire for the visions to appear.
In modern time it has been researched in 1882 by the classical scholar Fredric W. H. Myers. Since then it has been used by many people in more effective ways, just after a due training.