From: http://violet.berkeley.edu/~korea/tangun.html

	The Wei Shu tells us that two thousand years 
ago, at the time of emperor Yao, Tangun Wanggôm 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 Wanggôm.

	In the fiftieth year of the reign of Emperor Yao, 
Tangun made the walled city of P'yôngyang the capital 
and called his country Chosôn.  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 Chosôn, Tangun moved to Changdangyông, 
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)