The kyo-masu is a type of masu (measure) which was designated as the official masu from the late medieval period to the postwar period. Inside, a kyo-masu measures four sun and nine bu (about 14.8 centimeters) in both length and width, and two sun and seven bu (about 8.1 centimeters) in depth, which makes one sho, that is, 64,827 cubic bu; technically, however, these are the measurements of a 'shin Kyo-masu' (new Kyo-masu).
When the Enkyu senjimasu (the nation-wide official measure in the Enkyu era) established by the Imperial Court fell out of use as the political power of the court noble government declined, masu began to be manufactured by a variety of different standards around the country, and the negative effects of this situation worsened in the Muromachi period. When the standardization of masu was called for in the Warring States period, the masu known as the 'Kyoto jugo-masu' (the proper name for kyo-masu) came into use throughout the Kinai region. This became known as a 'kyo-masu,' for short. Nobunaga ODA, who came up to Kyoto in 1568, adopted the 'Kyoto jugo-masu' as the standard masu in his territories, and it was also adopted by Hideyoshi TOYOTOMI for use in deciding the initial official productivity estimates (kokumori) of Taiko Land Survey and in collecting land tax. From this time forward, Kyoto jugo-masu was considered the official masu. However, although theories differ, the Kyoto jugo-masu at the time is thought to have been smaller than the modern-day kyo-masu, measuring five sun (about 15.2 centimeters) in both length and width, and two sun and five bu (about 7.6 centimeters) in depth, which equaled 62,500 cubic bu (although another theory exists).
The need to maintain accuracy in measurement led to the setup of the Masu-za (monopoly bureau of masu) in Kyoto, which was supervised by Sakuzaemon FUKUI. On the other hand, Ieyasu TOKUGAWA, when transferring his clan to Edo, invited Tozaemon TARUYA from Totomi Domain (his former territory) to come to Edo, and left the manufacture of kyo-masu in Ieyasu's territories in his hands; this later developed into the Edo Masu-za and, after the formation of the Edo shogunate, was deemed as important as the Masu-za in Kyoto. As the Edo shogunate was formed, however, control of the Masu-za in Kyoto was relaxed, and the Kanei era saw the manufacture of kyo-masu measuring 64,827 cubic bu, which was larger than those of the Toyotomi government. For that reason, the Edo kyo-masu, which had been produced by traditional methods, came to be called 'Edo-masu,' and a difference was created. In light of the economic influences in Kyoto and Osaka, the Edo shogunate, in the name of the regulations for unifying kyo-masu unit, determined to designate the existing kyo-masu as official and to divide 66 provinces around the country into the East and West: the East and the West would be in charge of the Edo Masu-za and the Kyo Masu-za, respectively, each having the rights to the exclusive manufacture, sale and screening of kyo-masu, and the law allowed severe punishment for the manufacture and sale of fake masu. This is what is known today as a kyo-masu, but since it differs from the kyo-masu made in Edo during the Toyotomi government and the early Edo period, as stated above, it is sometimes called "shin-kyomasu" to distinguish from the previous kyo-masu.
There were two types of kyo-masu during the Edo period: the Tsurugane-masu (a masu for measuring grain), which had a steel bar fixed diagonally onto its upper edge, and the Kiji-masu (a masu for measuring liquid). Both came in seven types: one go, two and a half go, five go, one sho, five sho, seven sho, and one to. Though shogunal demesne and many domains purchased masu from their Masu-za to distribute in their own territories, some of the major historic domains held firmly to their ancestral masu, while others ordered their designated Masu-za, most of whom were merchants in the domain, to manufacture masu identical to kyo-masu, thus refusing the orders from the shogunate government; this custom is called 'han-masu' (masu of the domain). Since no domain was able to thrive economically without trading with Kyoto and Osaka, the center of kyo-masu territory, even the domain that maintained their own han-masu gradually began to manufacture masu that complied with kyo-masu. Not all clans and lords adopted kyo-masu, and some merchants used masu that were not kyo-masu for illicit purposes; this made the unification of masu extremely difficult.
The Meiji government adopted a policy of maintaining the shaku-and-kan measuring system (length by the shaku and weight by the kan) in 1870, but with the Meiji Weights and Measures Control Law in 1875, a decision was made to abolish Masu-za and to leave the manufacture and sale of masu to the private sector with calibration conducted by the government. Subsequently, when the metric system was implemented in 1959 and came into full use five years later, kyo-masu went completely out of use.