The earliest text speaking of "small dragon kings" is the (lost) book Liang sigong ji 梁四公記 that is quoted in the Song period 宋 (960-1279) encyclopaedia Taiping yulan 太平御覽. The small dragon kings live in a 50 li- (1 li being about 500 metres) deep cave south of Lake Dongting 洞庭湖 in a dragon palace (longgong 龍宮). They are controlled by the seventh daughter of the Dragon King of the Eastern Sea and guard a hoard of jewels.
The Dragon Lord (Longjun 龍君) of Lake Dongting is also mentioned in Li Chaowei's 李朝威 novella Liu Yi zhuan 柳毅傳 from the Tang period 唐 (618-907).
The Ming period 明 (1368-1644) romance Xiyouji 西遊記 speaks of the monkey Sun Wukong's 孫悟空 who forces the Dragon King of the Eastern Sea to deliver his jewels. Another dragon king, that of the River Jing 涇河, delivers rain at the wrong time and is therefore executed by counsellor Wei Zheng 魏徵 (580-643), at least in his dream. The Buddhist treasure that the dragon king of Lake Bibo 碧波潭 has stolen is brought back by Sun Wukong and his companions.
In this Ming period romance, the number and living places of the dragon kings is largely expanded to all the four seas, and even to lakes and ponds. Another Ming period novel, Wu Yuantai's 吳元泰 (fl. 1566) Dongyouji 東遊記, narrates how the Eight Fairies (Ba Xian 八仙) crossed the sea and fought with a dragon king.