What was the ritual of asking for rain in ancient times?

First of all, I study the history of the Song Dynasty, so I am familiar with the Song Dynasty. I can quote a passage from the History of Song Dynasty (volume 102) and the Rite of Five Prayers for your reference. I think other dynasties are similar. The record of the rain-praying ceremony will be recorded in the official etiquette of each dynasty, so you can refer to it.

The following is the record of Wu Zhi Song Shili:

(Song Zhenzong) After two years of drought in Xianping, a letter was sent to Lei Yu. Li Yong's "Pray for Rain" came out from the inside: in the first and second days, he chose the eastern soil as an altar, borrowed the soil to build a Qinglong, spent three days in the Dragon House, painted flowing water, set up incense tables, tea fruits and bait, and led a group of officials to the countryside to wish Zhu, and no music or witchcraft was allowed. The rain is enough to send dragon water. The rest of the square is like this, decorated with the colors of the square. Generally speaking, the mileage of daily drying and earth borrowing, the size of utensils and the repair of dragons are all divided into five elements. Grant the road.

In May of the third year, there was a drought in Jingdezhen, and the company published it by painting dragons and praying for rain. Methods: Choose Tandong or deep forest, and cooperate with Gengxu, Xinsi, Renchen, Guiri, Nianren, secretariat, commander-in-chief, fasting and cleaning. First tell the society to complete the order with pickled wine and build a three-story square altar, which is two feet high and one foot three feet wide, with 20 steps outside the altar and white rope as the boundary. Bamboo branches are inserted on the altar and painted with Zhang Hualong. The picture shows snakehead looking in all directions, surrounded by ten stars. White dragon in the middle, black cloud; Draw water waves, the tortoise looks around, spits black gas like a line, and the gold and silver dani adorns the dragon. Set the soap bucket, put the goose neck blood on the plate, sprinkle willow branches on the dragon, rain once every three days, offer sacrifices, pick up the dragon and throw it into the water. Dazhong Xiangfu suffered a drought for two years, and sent his secretary Tian Shaojian to the northern suburbs to worship Xuanming's five stars and remove the altar. It rained enough, so I sent an official to thank my country.

The ritual of praying for rain in the history of the Song Dynasty has been clearly recorded, and I hope it will help you.