During the Jin Dynasty, there was a young man named Che Yin who loved learning. His family was destitute, and they could not afford lamp oil for him to study at night, so he could only memorize texts by day.
One summer evening, while reading, he saw many fireflies lighting up the dark sky. An idea struck him: if he gathered many fireflies together, they might serve as a lamp. He found a white silk bag, caught as many fireflies as he could, and hung it up. The light was dim but sufficient for reading. From then on, he used fireflies as his lamp whenever possible.
Through diligent study, Che Yin eventually became a senior official. The idiom "Reading by the light of reflected snow or gathered fireflies" now describes those who persevere in their studies despite hardship.