When unification of the whole country was in process with the power of Nobunaga ODA and then Hideyoshi TOYOTOMI, there was the need to standardize the masu used nationwide in common, because the standard of the masu (or sho) affected the amount of nengu (land tax) paid by farmers.
織田信長から豊臣秀吉へという全国統一の流れの中で、納める年貢の量に直結する「升」を量るための枡を全国共通のものにする必要が生じた。