Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s5.35

v2.c12.s5.35

Instruments of the same type or with certain variations as those described by Bhāskarācārya are met with in the works of Brahmagupta and Lalla. ***But both of them have mentioned some additional instruments for finding time, viz. Kartarī, Kapāla and Pīṭha. The modern S. S. does not describe any instruments in detail ; still it has mentioned the names of the following instruments :—Swayam-waha; Gola, Śaṅku, Yaṣṭi, Dhanu, Cakra and Kapāla. It is interesting to note that the Pañca Siddhāntikā, Āryabhaṭīya, modern S.S. and Lalla-tantra do not anywhere mention the ‘Turiya yantra’.* It was Ptolemy among western astronomers who first invented the quadrant instrument. Before his time, they used the complete circular instrument for taking observations ; but later on, the Western astronomers began to use the quadrant instrument for all purposes. In modern times, however, the quadrant instrument has completely disappeared and the complete circle instruments have come into use in their place. Modern scholars accuse Ptolemy of having taken a retrograde step by introducing the quadrant instrument.** The purpose of mentioning this here is that while the quadrant instrument has been mentioned by Ptolemy, it was not known to our astronomers till śaka 500. It, therefore, proves that the Romaka Siddhānta is neither a translation of Ptolemy’s work nor has it been compiled on the basis of that work and that we knew nothing about Ptolemy’s work, till at least Śaka 500. The same thing was seen before from our study of the Romaka Siddhānta (Page 12). One more important thing which comes to our notice is that all our instruments have been invented by our astronomers quite independently ; and the quadrant instrument which came into use later on, was also independently invented. It could have been easily suggested by the ‘cakra’ and cāpa instruments ; and since it occurs for the first time in Brahmagupta’s work, it must have been invented by him.***