The spokes of a wheel are also often used as symbols of the Buddhist doctrine of dependent origination. According to the Theravada scholar Buddhaghosa:“It is the beginningless round of rebirths that is called the ’Wheel of the round of rebirths’ (saṃsāracakka). Ignorance (avijjā) is its hub (or nave) because it is its root. Ageing-and-death (jarā-maraṇa) is its rim (or felly) because it terminates it. The remaining ten links Dependent Origination are its spokes saṅkhāra up to the process of becoming, bhava.” The earliest Indian monument featuring dharmachakras are the Ashokan Pillars, such as the lion pillar at Sanchi, built at the behest of the Mauryan emperor Ashoka. According to Benjamin Rowland: ”The Sārnāth column may be interpreted, therefore, not only as a glorification of the Buddha’s preaching symbolised by the crowning wheel, but also through the cosmological implications of the whole pillar as a symbol of the universal extension of the power of the Buddha’s Law as typified by the sun that dominates all space and all time, and simultaneously an emblem of the universal extension of Mauryan imperialism through the Dharma. The whole structure is then a translation of age-old Indian and Asiatic cosmology into artistic terms of essentially foreign origin and dedicated, like all Asoka’s monuments, to the glory of Buddhism and the royal house.”According to Harrison, the symbolism of "the wheel of the law" and the order of Nature is also visible in the Tibetan prayer wheels. The moving wheels symbolize the movement of cosmic order ("ṛta").