[伊索寓言] 背盐的驴

The Donkey Loaded with Salt

There was once a huckster(叫卖的小贩) who kept a donkey, and when he heard that some cheap salt was being sold at the seaside, he drove his donkey there to buy some.  After having loaded the donkey with as much salt as it could carry, the huckster drove him home alongside a slippery ledge(边缘) of rock, until the donkey accidentally fell into the river below...they crossed the river into which the donkey had previously fallen, and this time he slipped into the water on purpose...he placed a load of sponges(海绵) on the beast...But the sponges became soaking(浸湿的) wet, and the donkey discovered to his dismay(沮丧) that his burden had doubled its weight instead of getting lighter.

The same poly will not suit all circumstances.