Li Yu (1611–1680), with courtesy name Lihong, styled himself as the bamboo-hat man on the Lake, and was a native of Lanxi (present Lanxi, Zhejiang Province). He lived in Nanjing and Hanzhou most of the time. His works Casual Expressions of Idle Feeling touched upon sound and appearance, living room, food and drink, and vessels for enjoyment, and so on. It was a monograph on aristocratic class in feudal society pursuing hedonic life. However, the two parts, that is, On Lyrics and Drama and On Performance Practice, touched upon all aspects of drama creation and stage performance. Although they were also aspects of the hedonic life of feudal literati, they were systematic in content and unique on some specific issues, so their academic value was high.