<span>There is likewise another diversion which is only shown before the emperor and the empress, and first minister, upon particular occasions. The emperor lays on the table three fine silken threads of six inches long; one is purple, the other yellow, and the third white. These threads are proposed as prizes for those persons whom the emperor has a mind to distinguish by a peculiar mark of his favor. . . . The emperor holds a stick in his hands, both ends parallel to the horizon, while the candidates advancing, one by one, sometimes leap over the stick, sometimes creep under it, backward and forward, several times, according as the stick is advanced or depressed. </span>
I think the answer would be: <span>The emperor rewards his subjects for jumping over and under a stick.
The full passage basically tell the readers about the strange contest that both the emperor and the empress like to conduct. We can see from the third sentence that those who are able to finish emperor's contest will be rewarded with a thread of silk.</span>
