The Wei Shu tells us that two thousand years ago, at the time of emperor Yao, Tangun Wangg˘m chose Asadal as his capital and founded the state of Chos&circon. The Old Record notes that in olden times Hwanin's sone, Hwanung, wished to descend from heaven and live in the world of human beings. Knowing his son's desire, Hwanin surveyed the three highest mountains and found Mount T'aebaek the most suitable place for his son to settle and help human beings. Therefore he gave Hwanung three heavenly seals and dispatched him to rule over the people. Hwanung descended with three thousand followers to a spot under a tree by the Holy Altar atop Mount T'aebaek, and he called this place the City of God. He was the Heavenly King Hwanung. Leading the Earl of Wind, the Master of Rain, and the Master of Clouds, he took charge of some three hundred and sixty areas of responsibility, including agriculture, allotted lifespans, illness, punishment, and good and evil, and brought culture to his people. At that time a bear and a tiger living in the same cave prayed to Holy Hwanung to transform them into human beings. The king gave them a bundle of sacred mugworts and twenty cloves of garlic and said, "If you eat these and shun the sunlight for one hundred days, you will assume human form." Both animals ate the spices and avoided the sun. After twenty-one days the bear became a woman, but the tiger, unable to observe the taboo, remained a tiger. Unable to find a husband, the bear-woman prayed under the alter tree for a child. Hwanung metamorphosed himself, lay with her, and begot a son called Tangun Wangg˘m. In the fiftieth year of the reign of Emperor Yao, Tangun made the walled city of P'y˘ngyang the capital and called his country Chos˘n. He then moved his capital to Asadal on Mount Paegak, also named Mount Kunghol, whence he ruled for fifteen hundred years. When, in the year
kimyo[1122 BC], King Wu of Chou enfeoffed Chi Tzu to Chos˘n, Tangun moved to Changdangy˘ng, but later he returned and hid in Asadal as a mountain god at the age of one thousand nine hundred and eight.
Translated by Peter H. Lee. (http://violet.berkeley.edu/~korea/legends.html#phl)