Monsoon rainfall cycles as depicted in ancient Sanskrit texts
Year to year variation of Indian monsoon rainfall is described qualitatively in some ancient Sanskrit texts. Interestingly, these are cyclic with periods of 3, 5, 7, 18 and 60 years. Time series analysis of actual seasonal rainfall data shows that at very near the above periods the spectrum has significant peaks. The Venus visibility portent stated in the Arthasastra appears to be a proxy for the near three-year fluctuation cycle in the rainfall.