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Late Imperial developments

The word "abacus" was first mentioned by Xu Yue(160–220) in his book suanshu jiyi (算数记遗), or Notes on Traditions of Arithmetic Methods, in Hang Dynasty. As it described, the original abacus had five beads (suan zhu) bunched by a stick in each column, separated by a transverse rod, and arrayed in a wooden rectangle box. One in the upper part represents five and each of four in the lower part represents one. People move the beads to do the calculation.

In 15 century, abacus came into its suan pan form and overtook the counting rods and became the preferred computing device, spreading among merchants to the other countries. It is easy to use and carry, which also provides fast and accurate operation. Zhu Zaiyu, Prince of Zheng who invented the equal temperament used 81 position abacus to calculate the square root and cubic root of 2 to 25 figure accuracy.

Abacus-based Mental Calculation

By learning how to calculate with abacus, the one can can improve his mental calculation which becomes faster and more accurate in doing large number calculations. Abacus‐based mental calculation (AMC) was derived from the abacus which means doing calculation, including addition, subtraction, multiplication, and division, in mind with imaged abacus. It is a high-level cognitive skill that run through calculations with an effective algorithm. People doing long-term AMC training shows higher numerical memory capacity and more effectively connected neural pathways. They are able to retrieve memory to deal with complex processes to calculate. The processing of AMC involves both the visuospatial and visuomotor processing which generate the visual abacus and perform the movement of the imagery bead. Since the only thing needed to be remembered is the finial position of beads, it takes less memory and less computation time.

Disappearance

The Yongle Dadian was not printed for the general public, because the treasury had run out of funds when it was completed in 1408. It was placed in Wenyuan Ge (文渊阁) in Nanjin after completed until 1421 Yongle Empire moved the capital to Beijing. In 1557, during the reign of the Jiajing Emperor, the encyclopedia was narrowly saved from a fire that burnt down three palaces in the Forbidden City. A manuscript copy was commissioned by Jiajing Emperor in 1562 and completed in 1567. The original one was lost after duplicated. There are three major theories for the lost, but no conclusion was made:

Destroyed in late Ming Dynasty

Buried with Jiajing Emperor

Burned in Qianqing Palace fire

The original manuscript of the Yongle Dadian was almost completely lost by the end of the Ming dynasty, but 90 percent of the 1567 manuscript survived until the Second Opium War in the Qing dynasty. In 1860, the Anglo-French invasion of Beijing resulted in extensive burning and looting of the city, with the British and French soldiers taking large portions of the manuscript as souvenirs. 5,000 volumes remained by 1875, less than half of the original, which dwindled to 800 by 1894. During the Boxer Rebellion and the 1900 Eight-Nation Alliance occupation of Beijing, allied soldiers took hundreds of volumes, and many were destroyed in the Hanlin Academy fire. Only 60 volumes remained in Beijing.