Two alternative arrangements of the sixty-four hexagrams of the I Ching, the Book of Changes. Each line is either broken, representing Yin, or unbroken, representing Yang, though each figure is generally seen as being composed of two trigrams.
The cycle of the hexagrams does not follow a single inevitable sequence in quite the same way as the Phases of the Moon, and complete Yin and complete Yang are generally classified as the first two hexagrams in any treatment.
The following comments are purely speculative and have no basis in the Yeatses' writings or the Automatic Script. However, it might be noticed that, in the traditional square arrangement of the hexagrams, the number of hexagrams at the outer edge is 28. These are the combinations of the two 'pure' hexagrams—Ch'ien, three Yang lines, and K'un, three Yin lines—as both upper and lower trigrams.
The hexagrams are traditionally arranged in pairs, which correspond and contrast in varying ways, so that one can draw lines between the pairs to show the connections.