Who is the author of "Yan Gu Zhao Zi" calligraphy

Calligraphy in Ming and Qing Dynasties was more popular than before. Some people describe it as a three-foot boy in the Ming Dynasty, who can write a book with a pen. At that time, calligraphy was good at running script and cursive script, and a number of calligraphers such as Dong Qichang emerged. Dong Qichang's calligraphy absorbed the essence of ancient calligraphy, but it was not deliberately imitated in his notes, and it had the beauty of "Yan Gu Zhao Zi".