Shunga was heavily influenced by illustrations in Chinese medicine manuals beginning in the Muromachi era (1336 to 1573). Zhou Fang, a notable Tang-dynasty Chinese painter, is also thought to have been influential. He, like many artists of his time, tended to draw genital organs in an oversized manner, similar to a common shunga topos. Besides ""shunga"" literally meaning a picture of spring (sex), the word is also a contraction of "shunkyū-higi-ga" (春宮秘戯画), the Japanese pronunciation for a Chinese set of twelve scrolls depicting the twelve sexual acts that the crown prince would perform as an expression of yin yang.