The Yogasūtras of Patañjali (200 B.C.) is an accredited work on the philosophy and practise of Yoga. The third chapter of this work designated as Vibhūti-pāda (the section dealing with supernatural powers) gives an account of many yogic powers and the means of attaining them. One such power mentioned there (3.44 and 45) is ‘bhūtajaya.’
Bhūtas are the five elements: pṛthvī or earth, ap or water, tejas or fire, vāyu or air and ākāśa or ether. When a yogi practises saṁyama on them, he conquers them.
Saṁyama is the technical name given to the trio of dhāraṇā (fixing the mind on the object of concentration), dhyāna (meditation) and samādhi (superconscious revelation).
If saṁyama is achieved on the bhūta pṛthvī or earth, he conquers it. As a result, the solidity of the earth will not be an obstacle to his free movement. Similarly the conquest of the bhūta water gives him immunity against wetness, of fire, immunity against burning and so on.