A mikvah must, according to the classical regulations, contain enough water to cover the entire body of an average-sized man; based on a mikvah with the dimensions of 3 cubits long, 1 cubit wide, and 1 cubit deep, the necessary volume of water was estimated as being 40 seah of water[6][7]. The exact volume referred to by a seah is debated, and classical rabbinical literature only specifies that it is enough to fit 144 eggs[8]; most Orthodox Jews use the stringent ruling of the Avrohom Yeshaya Karelitz, according to which one seah is 14.3 litres, and therefore a mikvah must contain approximately 575 litres[9]. This volume of water could be topped up with water from any source[10], but if there were less than 40 seahs of water in the mikvah, then the addition of 3 or more pints of water from an unnatural source would render the mikvah unfit for use, regardless of whether water from a natural source was then added to make up 40 seahs from a natural source[11]; a mikvah rendered unfit for use in this way would need to be completely drained away and refilled from scratch[12].