At the age of 29, Prince Siddartha renounced all the worldly comforts and left Kapilavastu through the eastern gate of the palace. After witnessing Chatur Nimitta Darshan (four causative sights), Siddhartha made a silent pledge to find the path of salvation for the sentient beings. He renounced his family and royal lineage and one night, he left the palace secretly on his horse Kanthaka with the help of his charioteer Chhanna through the Eastern Gate (Mahaviniskramana Dwara) in a quest for enlightenment. This event is recorded as Mahaviniskramana or the Great Renunciation, one of the twelve deeds of Lord Sakyamuni Buddha in the Buddhist scriptures.
As Prince Siddhartha grew older, he increasingly became curious about the world outside the palace walls. On one fateful day, the prince asked his charioteer Channa to take him outside the palace. During the journey, he came across the sights of an old man, a diseased man and a dead body being carried away for a funeral, followed by a group of weeping mourners. Deeply shocked, when the prince asked Chhanna about these sightings, his courtier replied that everybody gets old if not died young, anybody may fall sick and no one can escape from the death. The prince sighed, "is this the happy world they brought me forth to see". He also saw a wandering saint; clam, peaceful, and undeterred by these human sufferings. Chhanna told the troubled prince that the saint had renounced the world and was seeking a lasting liberation from these sufferings. Despite all the precautions, King Suddhodhan could not keep his son oblivious to the inevitable human sufferings.
The prince returned to his palace in deep contemplation. He could not set his mind free from the sights he had seen outside the palace. He also got the message that his wife Yasodhara had just given birth to a baby boy. King Suddodhana named his grandson as Rahula and organized grand festivities. But Prince Siddhartha did not participate to celebrate but uttered, “a fetter is set upon me”. His life at the palace became increasingly agonizing and unbearable.
After witnessing Chatur Nimitta Darshan (four passing sights), one night, when his wife Yasodhara and son Rahula were asleep, Prince Siddhartha, at the age of 29, embarked upon his quest for salvation. Accompanied by Channa and his favorite horse Kanthaka, he quietly left Tilaurakot palace from the eastern gate and reached river Anoma the next morning. The prince dismounted from horse, put off his royal robes and jewelry and handed them to Chhanna and asked him to return. Channa took the prince’s belongings back to the palace. Chhanna, with a very heavyheart and in tears, made farewell and left for Kapilavastu with Kanthaka. It is believed that the horse dropped dead out of grief in front of the eastern gate and was reborn as a disciple of Lord Sakyamuni Buddha. An earthen mound dedicated to Kanthaka is still there, a few meters away from the eastern gate of Tilaurakot palace. Chinese traveler Hiuen Tsang mentions about a commemorative stupa of Kanthak east to the Mahaviniskramana Dwara.