Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v1.c5.86

v1.c5.86

We have no clue for ascertaining whether there were any works more ancient than the Vedāṅga Jyotiṣa and the Saṃhitās of Garga and others. None of these are available at present. Nor can we say with any degree of certainty whether the Saṃhitās of Garga and others that are available at present, have all retained their original composition and structure. In the case of Garga Saṃhitā some two or three versions are available. Nevertheless, it is evident that some Saṃhitā works containing a treatment of all the three branches together must have been in existence at one time, as is evident from the above quotation from Varāhamihira, let alone be the question whether such treatment was complete in itself or only fragmentary. As the knowledge of astronomy was progressing and as each branch was nearing perfection, different works, each devoted to some specific branch, came to be written and the term Saṃhitā was then exclusively applied to one branch in particular. Varāhamihira's Pañcasiddhāntikā shows that there were independent works on the different branches written before his time (i.e., before Śaka year 427). Āryabhaṭa's work, which deals exclusively with Gaṇita, belongs to a slightly earlier date than that of Varāhamihira. It will, however, be shown in detail, in the following pages, that the Gaṇita branch had become independent at a still earlier date. As for Varāhamihira himself, he has to his credit independent treatises on all the three branches.