In the past, the grains like rice were sold and bought by the volume – at least at the retail level. The two main units of volumetric measure used were the “Cupak” and the larger “Gantang”. 4 cupaks = 1 gantang.
Largely made of thick gauge galvanized iron sheets, these vessels had to – at least theoretically – comply to government standards. The shopkeeper would fill up one of these to the brim – usually a heap would be formed at the center – and then used a wooden scraper bar to level out with the rim. Well, we customers always tried to make some gains by gently rocking the vessels and tapping on them, to increase the packing density – much to the chagrin of the shopkeeper.
Nowadays, everyone seems to have switched to using weight measure, ie kilograms mostly.