Shu meant beans.
Cai Shu was actually "shu cai," meaning "gathered by beans"—or, more accurately, it was an opening phrase used by wizards when constructing spell formulas. "Shu" referred to hunters, while "shu cai" meant "hunting."
It metaphorically meant sending beans out to hunt.
The entire spell had evolved from the early wizards' "Scattering Beans into Soldiers." After generation upon generation of simplification and adjustment, the originally complicated rituals—such as setting up altars, chanting scriptures, drawing talismans, pacing the Dipper, and so on—had been incorporated into the refining process of Bean Soldiers, greatly simplifying the entire procedure.
When used, it only needed to be activated through the simple "Cai Shu" spell formula, making it easy to cast the originally high-level spell of Scattering Beans into Soldiers.
Zheng Qing's Bean Soldiers had been refined by himself.
While searching Sanyou Bookstore for traces left behind by his teacher, he had accidentally discovered Guo Gong's Dialects, written during the Eastern Jin by the great mage Guo Pu—equivalent to a modern Archwizard. It recorded the method for refining Bean Soldiers. At the time, a note had been tucked between its pages, containing his teacher's method for improving Guo Pu's Bean Soldiers.
In short.
His teacher had used a method similar to the way he had "modified" Zheng Qing into a Forbidden Curse. First, he selected a suitable piece of talisman paper and drew the basic Bean Soldier spell formula on it. Once the Rune was successfully drawn, the talisman paper automatically curled into a bean.
The Bean Soldier produced at this stage had a weak foundation and should really have been called a "paper soldier."
Then, using a short, sharp Chicken-Spur Brush and cinnabar mixed with the blood of the appropriate spirit beasts, he drew new Runes onto the bean's surface. For example, drawing