What are the basic concepts of two devices and four images?

1, two instruments: The word two instruments means "two appearances of planets" in classical Chinese, which represents the vague and abstract understanding of cosmic stars in ancient China. Originated from the ancient people's view of nature in China. The ancients observed various opposing and related natural phenomena in nature, such as heaven and earth, sun and moon, day and night, cold and heat, men and women, up and down, etc. And summed up the concept of "Yin and Yang" in a philosophical way of thinking. As early as the Spring and Autumn Period, Yin and Yang were mentioned in Yi Zhuan and Lao Zi's Tao Te Ching. The theory of Yin and Yang has penetrated into all aspects of China's traditional culture, including religion, philosophy, calendar, Chinese medicine, calligraphy, architecture, divination and so on. Yin and Yang are a division or subdivision of "unity of opposites or contradictory relationship", and they are species relations.

2. Four Elephants: In the early culture of China, the four elephants refer to Lao Yang, Shaoyin, Shaoyang and Laoyin in The Book of Changes, and also refer to the natural weather of the four seasons. After the Qin and Han Dynasties, it gradually referred to Qinglong, Baihu, Suzaku and Xuanwu, which originated from the ancient belief in stars and represented the stars in the east, west, south and north respectively. It was also called the Four Gods, the Four Celestial Spirits and the Four Holy Generals.