With all politeness, Gautama then left these two teachers and resolved to seek the highest Truth for himself. It was in that mood, with that spirit, that he walked from Rajagrha to the place which is today known as Buddha Gaya in the jungles of Uruvela. Having gone there, he established himself in a course of severe austerity, penance, and inward contemplation. Five other devotees were also engaged in the same pursuit in the place. They recognized the advanced spirituality of Gautama and accepted him as their spiritual guide and leader and followed him in his path of austerities. It was a path that was well defined and followed by various sadhakas of the time, a path consisting of severe austerity of body and mind. It was a form of extreme, rigorous ascetism. Gautama was a thoroughgoing person. If he accepted a procedure, he would not rest content till he thoroughly saw to the end of it. So he was foremost among the six seekers in the practice of austerity and mortification, until he became extremely weak from his fastings and privations.
Seeing their leader’s rigour and determination, the five disciples became extremely happy and hoped that he would soon attain enlightenment. But one day, when Gautama was getting up from his seat, he fell down unconscious from weakness; regaining consciousness, the following thought arose, in his mind : ‘What foolishness! I am in search of the highest Truth. It is a search that calls for the utmost courage and stamina, and yet I am weakening my body, weakening my senses, the only instruments I possess by which I can undertake this voyage of discovery; I shall not proceed on this path of foolish mortification any more.’
So he immediately forsook the path of senseless austerity, and proceeded to a nearby village for a food. Seeing Gautama abandoning the path of ascetism, the five disciples felt that their leader had strayed into the path of luxury and ease and decided that he was not worthy of them; they deserted him. Gautama did not mind their desertion. He went to the village and received a bowl of payasa or sweetened milk-rice from a village girl by name Sujata; he bathed in the nearby river, ate the payasa and rested during the afternoon; and towards the evening he proceeded to a nearby spot where there was a large banyan tree, and sat under it with the determination not to rise till he had realized the highest Truth.
All these are in the line of what the Upanishads had prescribed. Sitting under the tree, with senses and mind under control, Gautama entered into the depths of meditation. His naturally pure mind, which had become purer as a result of the discipline he had undergone for six years was now so fine that with little effort he soared to the heights of meditation. In the first three watches of the night, Gautama plunged deeper and deeper into the depths of his being, and the descriptions of meditation given in the Buddhist scriptures tally with what the Vedanta describes as the process of entering into the nirvikalpa state of samadhi, the samadhi where the mind transcends the sphere of form, the sphere of consciousness and the sphere of duality, and ultimately goes into the highest realm where no personality exists, where existence is unconditioned and pure. Towards the foruth watch of the night, Gautama realized the highest Truth and attained bodhi, Enlightenment. He became Buddha, the Illumined.
The above excerpt is taken from Dynamic Spirituality for A Globalized World -- A commemorative volume of selections from the works of Swami Ranganathananda