In his commentary on the Oxherding Pictures—the Zen depiction of the progression to enlightenment

—Tibetan master Chogyam Trungpa wrote:

In the Tibetan tradition there is an analogy of elephant herding but it refers largely only to the practice of shamatha. The symbolism does not go beyond the riding of the elephant. In the oxherding pictures the evolutionary process of taming the bull is very close to the Vajrayana view of the transmutation of energy.

Great stuff, take a look at at the series at shambhala.org. And for more teachings on the Oxherding Pictures, look at Barry Briggs’s blog Ox Herding. Briggs practices and teaches in the lineage of Zen Master Seung Sahn.