यनतरलकषणम — What is a Machine? Bhoja's Definition and Fourfold Classification of Yantras

The thirty-first chapter of Bhoja's Samarāṅgaṇasūtradhāra (11th century CE), the Yantravidhāna, is the only extended Sanskrit treatment of machines in the śilpa literature. This article studies its opening verses: the benedictory image of the cosmos as a machine (31.1), the claim that machines serve all four aims of life (31.2), the two definitions of yantra (31.3–4), and the fourfold classification by mode of drive (31.10). Each verse is given in Devanāgarī and IAST with word-division and a literal translation, and its technical terms are mapped to modern engineering categories. The analysis shows that Bhoja defines a machine not by its parts or its purpose but by constraint: a machine takes forces that act "of their own accord" and compels them along a chosen path. This is the same insight that Franz Reuleaux placed at the foundation of modern kinematics in 1875. The fourfold classification is read as an early taxonomy of actuation, from self-acting devices to directly operated ones. Textual problems in the transmitted readings are noted throughout. Series: Yantravidhāna Studies, SSD-31/01.