From Handbook of Chinese Mythology by Yang Lihui and An Deming:
On the Tai Mountain in Shandong Province can be found a temple complex named Wangmu Pool. Most of it was built during the Qing dynasty. Every lunar March 3, a Saucer Peach Festival is held to celebrate Wangmu Niangniang’s [AKA Xiwangmu’s] birthday.
Pilgrims often try to throw coins into the basins in the center of the pool, believing that they will get the goddess’s blessing if they get them in. Some of them like to bring spring water back home, believing the divine water can keep them healthy.
I don’t have the page number on hand. If you have the book, it is at the end of the entry on Xiwangmu.