Baudhyana Shulbasutra describes a method of converting a square to a circle as:

तृतीयकरण्येन व्याख्याता| नवमस्तुभूमेर्भागो भवतीति||१.४७|| शुल्बसूत्

“Thereby is explained the tritiyakarani; it (the area produced by the tritiyakarani) is the ninth part of the area produced by the trikarani”.

Construct a unit square ABCD. Divide the square into 9 equal parts. Join AN to form diagonal of square AENK. Rotate AN about A such that it falls on AB at Q. Join points K and Q. Construct a square with KQ as side.