One day in hot summer, there was a donkey walking up on the mountain. The donkey brought several heavy sacks of salt on his back. He staggered along the hot shiny day, while his master was walking beside him.

"Oh, it's very hot. I think I can't walk any longer, carrying these heavy sacks of salt in this hot day..." said the donkey.

But in the front not far from him, he saw a river.

"Ah, there's a river! It would be better if I stop for a moment and drink. I'm so thirsty," said the donkey happily. In his excitement, he walked carelessly and suddenly...splash!!..he slipped and plunged into the river. He tried to stand up on the stone near him, but apparently he couldn't do it.

He tried to stand up for quite a long time. But strangely, the longer he was in the water, the lighter the burden on his back. Finally he could stand up easily.

"Good heavens, the salt is gone!" The master was very angry.

"Oh, I'm sorry...the salt is dissolved, I guess..." Donkey said innocently.

Several days later, the donkey undertook carrying sacks of salt again. As usual, he must walk beyond mountains with his master.

"Not long, there will be the river in the front," said the donkey by heart. When going crossed the river, the donkey fell and plunged into the river deliberately. The salt in the sacks he carried on his back was dissolved in water. 

"Great! So light!" Donkey hee hawed gladly.

However, the master apparently had learnt that the donkey did that deliberately, and he was very angry. "Lazy donkey!" The master said furiously.

The next day, the donkey undertook the task of carrying cotton. Once more, he walked with his master beyond mountains.

When arriving in the river, again and again the donkey ruined himself intentionally.

Splash…!!

See what had happened? The sacks of cotton became very heavy. Apparently the cotton absorbed water and to weighing the stone. Afterwards, the donkey must continue to go with the harden burden on his back. The donkey staggered under the intense sun shone while carrying the wet heavy cotton. It was even heavier than carrying the dry salt.