Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.3

v2.c12.s5.3

The word ‘vedha’ is derived from the root ‘vyadha’. Vedha is the name given to the act of observing the sun or anyother celestial body by holding a rod or a stick or some other object in between. Because the luminous celestial body is ‘struck’ by the rod, the act of observation has received the name “vedha”. The simple casting of a look at a celestial body is termed ‘avalokana’ (sighting); but this act also can be termed ‘observation’. Let us call this kind of observation ‘dṛṣṭivedha’ (i.e. look). The observation which is taken with the help of a stick or other means of taking observation, commonly known as ‘instruments’, should be termed ‘yantra-vedha’ (i.e. instrumental observation).