《明史·列传·卷一百七十三》
有次，在杨维桢家做客，有位客人拿出所赋《白燕诗》请大家看，凯微笑不语，另做一篇献与大家，维桢大惊，十分欣赏，给每个客人传阅，由此人们叫他 袁白燕 。
初，在杨维桢座，客出所赋《白燕诗》，凯微笑，别作一篇以献。维桢大惊赏，遍示座客，人遂呼袁白燕云。
Once, when he was a guest at Yang Weizhen's house, a guest took out a poem he had written, "Song of the White Swallows," and asked everyone to read it.  Kai smiled and said nothing.  He wrote another one and presented it to everyone.  Weizhen was greatly surprised and read it aloud for all the guests.  From then on, people called him "Yuan White Swallow."