By the time of Confucius in the late Zhou, gastronomy had become a high art. Confucius discussed the principles of dining: "The rice would never be too white, the meat would never be too finely cut. . . When it was not cooked right, man would not eat. When it was cooked bad, man would not eat. When the meat was not cut properly, man would not eat. When the food was not prepared with the right sauce, man would not eat. Although there are plenty of meats, they should not be cooked more than staple food. There is no limit for alcohol, before a man gets drunk. " During Shi Huangdi's Qin dynasty, the empire expanded into the south. By the time of the Han dynasty, the different regions and cuisines of China's people were linked by major canals and leading to a greater complexity in the different regional cuisines. Not only is food seen as giving "qi", energy, but food is also about maintaining yin and yang. The philosophy behind it was rooted in the I Ching and Chinese traditional medicine: food was judged for color, aroma, taste, and texture and a good meal was expected to balance the Four Natures ('hot', warm, cool, and 'cold') and the Five Tastes (pungent, sweet, sour, bitter, and salty). Salt was used as a preservative from early times, but in cooking was added in the form of soy sauce, and not at the table. The predominance of chopsticks and spoons as eating utensils also necessitated that most food be prepared in bite-sized pieces or (as with fish) be so tender that it could be easily picked apart.