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

In the third year of Shen-ch'ueh of Han,
In early summer, when the Great Bear (http://violet.berkeley.edu/~korea/legends.html#bear") Stood 
in the Snake,
Haemosu came to Korea,
A true Son of Heaven.
He came down through the air
In a five-dragon chariot,
With a retinue of hundreds,
Robes streaming, riding on swans.
The atmosphere echoed with chiming music,
Banners floated on the tinted clouds.
From oldest times men ordained to rule
Have come down from Heaven,
But in daylight he came from the heart of the sky--
A thing never before seen.
In the mornings he dwelt among men,
In the evenings he returned to his heavenly palace.
The ancients have told us 
That between heaven and earth the distance
Is two hundred thousand million
Eighteen thousand seven hundred and eighty ri.
A scaling-ladder could not reach so far,
Flying pinions could not bear the strain,
Yet morning and evening he went and returned at will.
By what power could he do it?

North of the capital was the Green River,
Where the River Earl's three beautiful daughters
Rose from the drake-neck's green waves 
To play in the Bear's Heart Pool.
Their jade ornaments tinkled,
Their flowerlike beauty was modest--
They might have been fairies of the Han River banks,
Or godesses of the Lo River islets.
The King, out hunting, espied them,
Was fascinated and lost his heart,
Not from lust for girls,
But from eager desire for an heir.
The three sisters saw him coming
And plunged into the water to flee,
So the King prepared a palace (http://violet.berkeley.edu/~korea/legends.html#trick)
To hide in till they came back:
He traced foudations with a riding whip:
A bronze palace suddenly towered,
Silk cushions were spread, bright and elegant,
Golden goblets waited with fragrant wine.
Soon the three maidens came in,
And toasted each other until they were drunk.
Then the King emerged from hiding;
The startled girls ran, tripped, and fell.
The oldest was Willow Flower,
And it was she whom the King caught.

The Earl of the River raged in anger,
And sent a speedy messenger
To demand, "What rogue are you
Who dares behave so presumptuously?"
"Son of the Heavenly Emperor," replied Haemosu,
"I'm asking for your noble daughter's hand."
He beckoned to Heaven: the dragon car came down,
And straightaway he drove to the Ocean Palace
Where the River Earl admonished him:
"Marriage is a weighty matter,
Needing go-betweens and gifts.
Why have you done these things?
If you are God's own heir,
Prove your powers of transmogrification!"
Through the rippling, flowing green waters
The River Earl leapt, changed into a carp;
The king turned at once into an otter
That seized the carp before it could move.
The earl then sprouted wings,
Flying upward, transformed into a pheasant;
But the king was a golden eagle
And struck like a great bird of prey;
The earl sped away as a stag,
The king pursued as wolf.
The earl then confessed that the king was divine,
Poured wine, and they drank to the contract.
When the king was drunk, he was put in a leather bag,
Set beside the girl in his chariot,
And set off with her
To rise to heaven together;
But the car had not left the water
Before Haemosu woke from his stupor
And, seizing the girl's golden hairpin,
Pierced the leather and slid out through the hole,
To mount alone beyond the crimson clouds.
All was quiet; he did not return.

The River Earl punished his daughter
By stretching her lips three feet long,
And throwing her into the Ubal stream
With only two maidservants.
A fisherman saw them in the eddies,
Creatures disporting themselves strangely,
And reported the fact to King Kûmwa.
An iron net was set in the torrent,
And the woman was trapped on a rock,
A monster of fearful appearance,
Whose long lips made her mute.
Three times they were trimmed before she could speak.
King Kûmwa recognized Haemosu's wife,
And gave her a palace to live in.
The sun (http://violet.berkeley.edu/~korea/legends.html#light) shone in her breast and she bore 
Chumong
In the fourth year of Shen-ch'ueh.
His form was wonderful,
His voice of mighty power.
He was born from a pottle-sized egg
That frightened all who saw it.
The king thought it inauspicious,
Monstrous and inhuman,
And put it into the horse corral,
But the horses took care not to trample it;
It was thrown down steep hills,
But the wild beasts all protected it;
Its mother retrieved it and nurtured it,
Till the boy hatched.  His first words were:
"The flies are nibbling my eyes,
I cannot lie and sleep in peace."
His mother made him a bow and arrows,
And he never missed a shot.

Years passed, he grew up,
Getting cleverer every day,
And the crown prince of the Puyô
Began to grow jealous,
Saying, "This fellow Chumong
Is a redoubtable warrrior.
If we do not act soon,
He will give trouble later."
So the king sent Chumong to tend horses,
To test his intentions.
Chumong meditated, "For heaven's grandson
To be a mere herdsman is unendurable shame."
Searching his heart, he sought the right way:
"I had rather die than live like this.
I would go southward (http://violet.berkeley.edu/~korea/legends.html#journey),
Found a nation, build a city--
But for my mother,
Whom it is hard to leave."
His mother heard his words
And wept; but wiped her glistening tears:
"Never mind about me.
Rather I fear for your safety.
A knight setting out on a journey
Needs a trusty stallion."
Together they went to the corral
And thrashed the horses with long whips.
The terrified animals milled about,
But one horse, a beautiful bay,
Leapt over the two-fathom wall,
And proved itself best of the herd.
They fixed a needle in his tongue
That stung him so he could not eat;
In a day or two he wasted away
And looked like a worn out jade.
When the king came around to inspect,
He gave this horse to Chumong,
Who took it, removed the needle,
And fed the horse well, day and night.
Then he made a compact with three friends,
Friends who were men of wisdom;
They set off south till they reached the Om,
But could find no ferry to cross.
Chumong raised his whip to the sky,
And uttered a long sad plaint:
"Grandson of Heaven, Grandson of the River,
I have come here in flight from danger.
Look on my pitiful orphaned heart:
Heaven and Earth, have you cast me off?"
Gripping his bow, he struck the water:
Fish and turtles hurried, heads and tails together,
To form a great bridge,
Which the friends at once traversed.
Suddenly, pursuing troops appeared
And mounted the bridge; but it melted away.
A pair of doves brought barley in their bills,
Messengers sent by his mysterious mother.
He chose a site for his capital
Amid mountains and streams and thick-wooded hills.
Seating himself on the royal mat as King Tongmyông,
He ordered the ranks of his subjects.
Alas for Songyang, king of Piryu,
Why was he so undiscerning?
Was he a son of the immortal gods,
Who could not recognize a scion of Heaven?
He asked Tongmyông to be his vassal,
Uttering rash demands,
But could not hit the painted deer's navel,
And was amazed when Tongmyông split the jade ring;
He found his drum and bugle changed
And dared not call them his;
He saw Tongmyông's ancient pillars,
then returned home biting his tongue.
So Tongmyông went hunting in the west,
Caught a tall snow-white deer,
Strung it up by the hind feet at Haewôn,
And produced a great malediction:
"Let Heaven pour torrents on Piryu,
And wash away his capital.
I will not let you go
Till you help me vent my wrath."
The deer cried with sounds so piteous
They reached the ears of Heaven.
A great rain fell for seven days,
Floods came like Huai joined with Ssu;
Songyang was frightened and anxious.
He had thick ropes stretched by the water,
Knights and peasants struggled to clutch them,
Sweating and gaping in fear.
Then Tongmyông took his whip
And drew a line at which the waters stopped.
Songyang submitted
And thereafter there was no argument.
A dark cloud covered Falcon Pass,
The crests of ridges were hidden,
And thousands upon thousands of carpenters
Were heard hammering there.
The king said, "Heaven for me
Is preparing a fortress up yonder."
Suddenly the mist dispersed
And a palace stood out high and splendid, 
Where Tongmyông ruled for nineteen years,
Till he rose to heaven and forsook his throne.

Translated by Richard Rutt.