《太平广记·卷一百九十七·博物》
从前，周公在洛阳，常把盛酒的器具放在河上，饮酒取乐，所以古诗中说，羽觞随东流。
昔周公城洛邑，因流水以泛酒。故逸诗云：羽觞随东流。
In the past, the Duke of Zhou in Luoyang often placed wine utensils on the river and drank for pleasure, so the ancient poem says, Yu Shang drifted on the east flow.