The iconographic origin and development of the Buddhist Triad format
In Buddhist art, two different ways of worshipping Shakayamuni have led to the emergence of two types of the triad format. From the Dharma cult, due to which the Dharma (the truth) is the essence of Buddha, has sprung the format of the Buddha surrounded by two attendants. In the context of Mahayana Buddhism, these attendants came to be represented as Mahayana Bodhisattvas. The Buddha cult, according to which there had been many other Buddhas before the birth of Shakyamuni, has given rise to a format showing three Mahayana Buddhas. They could stand for the three periods past, present and future, for three of the four directions or the three bodies (Trikaya) of the Buddha.