一叶报秋

Explanation: Subtle metaphor for individual signs, you can see the whole situation and development trend of the results. With the rather critical. " 　　Source: Tang Bao Rong "beginning see Ermao" Poetry rivers to go to sea to get damp easily, go tree leaf fall reported difficulty. "Tang Liushi" willow leaves, "the word wind Hubao leaf fall, even if the monarch to Qi worthy off."