The idiom "Catching Fireflies and Reading by Snowlight" originates from the Jin Dynasty. "Catching Fireflies" refers to Che Yin, who came from a poor family and could not afford lamp oil but wanted to study at night, so he caught fireflies in the summer to use as light. "Reading by Snowlight" refers to Sun Kang, who used the reflection of snow to read during winter nights. Later, the idiom came to symbolize diligent studying despite poverty.
During the Jin Dynasty, Che Yin was studious from a young age, but his family was poor, and his father could not provide proper learning conditions. To sustain basic needs, there was no extra money to buy lamp oil, so he had to use limited time to recite poetry and texts. One summer night, while reciting in the courtyard, he noticed many fireflies flying at low heights, their flashing lights standing out in the darkness. He thought, if he gathered many fireflies together, wouldn't they form a lamp? So he took a white silk bag, caught several dozen fireflies and put them inside, then tied the bag and hung it up. Although the light was dim, it was just enough to read by. From then on, whenever there were fireflies, he would catch some to use as a lamp. Thanks to his diligence, Che Yin later became a high-ranking official.