The Qian Trigram represents the sky, clarity, and movement. It is the extreme of Yang energy and represents the original spirit of people.
The Li Trigram represents fire and the sun, it has a broken yin line inside of Yang and represents our consciousness, which is both made up of nature (the outside Yang lines) and feeling (the inside yin line). It also refers to the heart (Yang) and the oxygen in our blood (Yin).
The Kan Trigram represents water. It has two broken yin lines with a yang line inside it and also represents out kidneys. The solid line represents life energy which is hidden deeply within us.
The Kun trigram represents earth and the corporeal body. Any physical form without movement is represented by this element and it is considered to be representative of death but also as the root of life.
These four trigrams are very important in meditation theory, since our goal is to abandon ourselves to the deep yin state of the earth trigram in order to cause the latent energy within the water trigram to shift and replace the yin energy of the fire trigram, thus changing out regular consciousness from the mind of consciousness and emotions, to the mind of pure consciousness, in which emotional feeling is replaced with the feeling of life energy.
Because the mind has latent feeling, which is yin and considered to be heavy, we can use this feeling to allow the consciousness to sink and become heavy, allowing the latent energy hidden within the water trigram to rise up, thus allowing us to attain vitality and awareness of universal reality not polluted by our thoughts and feelings.