स्वयंवाहकयन्त्राणि — Self-moving and Time-keeping Devices

Bhoja ranks the "self-moving" machine (svayaṃvāhaka) highest among the four classes of machines (31.10–11, discussed in Article 1), and he names time as one of the things a machine can be built to produce (31.51–54). This article brings together the passages of chapter 31 of the Samarāṅgaṇasūtradhāra that describe machines acting by themselves over time: a bed that rises one floor in each watch of the day (31.65–66ab); a plate whose "teeth" turn in sequence while a figure at its centre announces every nāḍī (31.66cd–67ab); a sphere that turns day and night showing the courses of the sun and planets (31.69cd–70ab); and a figure of a man riding an elephant who turns with each nāḍikā and strikes at its end (31.70cd–71ab). Read in modern terms, these are clock-driven devices: a time base, very probably a water-clock, drives a toothed wheel, and the wheel drives an indicator or a striking figure. The last device has a striking parallel in al-Jazarī's famous Elephant Clock (1206). The article also explains what Bhoja means by "self-moving", distinguishes it from the later Indian idea of a perpetual-motion wheel (svayaṃvaha), and places Bhoja's clocks within the Indian tradition of the ghaṭikā-yantra and the astronomical sphere. Article 9 of the series Yantravidhāna Studies (SSD-31), on chapter 31 of Bhoja's Samarāṅgaṇasūtradhāra. Verses discussed: 31.10–14, 31.51–54, 31.65–71. Web version: sanskritmanthan.in/a/ssd-31-09-svayamvaha-kala