Emperor Li Shimin of the Tang Dynasty cruises to a trip to Mount Tai. Li Shimin chose to set up camp in a place in the plains of southwestern Lu. As night fell, Li Shimin went into a dream, and dreamed that Bixia Yuanjun - the guardian deity of Mount Tai, dressed in gorgeous fairy clothes and riding a divine beast, led all the fairies to come and greet him. In the dream, Bixia Yuanjun invited Li Shimin to tour the immortal world and showed him the mystery and greatness of Mount Tai. When Li Shimin woke up, the sky was already light, and he immediately sent someone to gather earth and twist grass to make incense, and burned incense to worship.