Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c14.28

v2.c14.28

∗ *Ever since Śaka 1815, the author has devoted considerable thought and effort in the light of Patvardhan's art to decide the question whether the sāyana or nirayana system is true to nature so far as astrology is concerned. But no decision seems to be possible for the present. The positions of some planets, discerned by Patvardhan from physical traits are relative. For instance, he comes to know after reading the face, that there is a difference of 2° between the sun and Mercury or that a particular planet occupied a particular place from the ascendant. This does not lead to any decision. A still more important point is that the indications now established by Patvardhan were first based on Keropant's Patvardhanī Pañcānga. For example, he observed in a number of cases that a particular feature was connected according to Patvardhani Pañcānga with a certain degree on the ascendant or a certain degree denoted by a particular planet and then made it a rule to link that degree with the ascendant or planet in appropriate cases. He could as well have established such rules on the basis of the sāyana almanac from the very beginning. If people well-versed in Patvardhan's lore and able to understand the difference between sāyana and nirayana systems would continually toil for keeping a record for five or six centuries, the difference in the sāyana and nirayana positions of planets show an excess of 18° over the (nirayana) positions which Patvardhan sets down from the physiognomy of the native. If after 600 years it is noticed that, maintaining Patvardhan's rules, the difference between the positions of planets as found from physical features and the sāyana positions comes to 18° degrees only, the natural system for astrological purposes would prove to be a sāyana, and if it comes to 26°, then it would prove to be purely sidereal (i.e. nirayana). While reading horoscopes, Patvardhan adopts the nirayana signs of exaltations and ownership, as also the nirayana signs occupied by the planets and the ascendant. Nothing, however, can be decided from this.