Is there such a thing as throwing the holy grail in Buddhism?

This is not a matter of Buddhism, but a matter of Taoism. It is called "Jiao Cup" (pronounced "Jiao") and is usually made of bamboo roots of Dendrocalamus latiflorus and cut in half to predict the quality of lottery tickets. For example, after drawing lots, throwing a cup on the ground and judging whether it is good or bad according to the difference between positive and negative is one of the ancient divinations in China.

Throw a cup, a pair of hexagrams consists of two cups of yin and yang. Once you throw two upward hexagrams, it is called Yang hexagrams; Throw two hexagrams, the arc is upward, which is called yin hexagrams; Cast a divinatory image with a plane upward and an arc upward, which is called a holy divinatory symbol.

Divination method: to ask a god about something or a reason, you must first burn incense and pray and state the reason. Then hold a cup tip in your right hand and throw it up slightly, and divination will naturally fall to the ground, and one of the holy grail divination images will appear. Generally, a Taoist temple asks for good or bad luck, and the holy divination is auspicious, while others are fierce. Some people throw it three times and get a combination of hexagrams. Then, according to the combination of hexagrams, find the content of hexagrams and judge the good or bad of things.