"The 10 Heavenly Stems & 12 Earthly Branches." These two diagrams of the left hand were first published in a medical text the physician Liu Wenshu presented to the emperor in 1099 during the Northern Song dynasty.

'Understanding is Within One's Grasp' (Liaoran zaiwo): The Cultural History of Chinese Hand Mnemonics, Calculation, and Divination.

General Introduction

Hands communicate today among the deaf through different sign languages, between the brokers at the stock exchange, through the actions of mime, theatre and dance performers, by the hand signals of umpires, and in many other arenas where visual gesture substitutes for auditory signal and spoken word. Nevertheless, in the modern age we rarely see people using their hands to remember, to count, or to divine. The most obvious exception may be palm reading, which remains as alive today throughout the world as it was in the past.

One may still see children use their fingers to recall the numbers from one to ten or follow the rise and fall of their knuckles to work out whether a month is long (on the hump) or short (in the valley). You may have once tied a string around a finger to remind you of something you might have otherwise forgotten. There are also other less obvious exceptions. Perhaps you move your left thumb in a spiral around the twelve divisions of the fingers of your left hand counting breaths to help you focus during meditation, as one popular book on yoga recommends. Weight watchers also suggests that you use the size of your palm to ration your portions of meat and to make a fist as a guide to the size of vegetables and fruit per meal. The hand also figures prominently as the hamsa, or the hand of fatima, in the jewelry, key chains, magnets, and mezuzah’s found in Judaica gift shops to ward off the evil eye and thus protect the bearer.

In the present century, people in other parts of the world, especially in East Asia, continue to use their hands as a simple calculator and a mnemonic device. Similar practices, once common in medieval and early modern Europe, have practically disappeared in the western cultural sphere. Instead of hand mnemonics, calculations, and predictions, we now have the palm pilot. In lieu of using our imagination to project numbers, symbols, characters, and words onto the natural divisions of our palm, we use a hand computer. Instead of mnemonics and the arts of memory, we rely on electronics and data entry. Recovering how the hand was once a repository and means for acquiring knowledge in China, we can learn how ancient arts of memory placed understanding within the individual’s own grasp.

See one page article on hands in Chinese culture. "Nuance in Motion and Language"
(Taijiquan Journal 3.2 (Spring 2002): 1.

See online exhibition on hand symbolism and mnemonics in Europe originally
held at The Trout Gallery at Dickinson College, Sept-Nov 2000:
Writing on Hands: Memory and Knowledge in Early Modern Europe