Li Beihai, a young man from the Southern Song Dynasty, embraced the desire to measure and improve the real world with the "learning of arithmetic". He broke away from the rigid imperial examination system and traveled to the southeastern coast: in Mingzhou, he used geometric magic to help ships get out of trouble, and learned the art of navigation and astrology; in Quanzhou, he pioneered the "Dragon Gate Account" to clarify the capital of giant merchants, but was unable to compete with the greed for profit; in Guangzhou, he used fluid mechanics to improve bronze molds. He saved the craftsmen from disaster; he went to Hangzhou's "Jinxiu Fang" to use actuarial calculations to improve the weaving efficiency, but it ended up being a tool abandoned after capital extraction; in the end, he witnessed the absurd nature of the bureaucracy's use of numbers to whitewash peace and create lies at the household department in Bianliang. In the dusty library, Li Shande was as skilled in calculation as the Tang Dynasty but could not escape the fate of lychee transshipment, which resonated with Li Shande from this life and was completely disillusioned. He saw that there was no place for "calculating swordsmen" in temples, rivers and lakes, so he resolutely took the manuscript of "New Methods of Maritime Business Calculation", which condensed his life's practical wisdom, and decided to go eastward, casting his gleaming light on the fireworks of the market and the vast unknown sea, seeking the ultimate salvation and freedom of the soul.
