The original yakutian kumis is differed with it's strength and it's made only with cow's milk. To produce it they used a tightly closed leather vessel - simiir, which was made from the leather of an adult horse and they connect it with scrapings inside. The leather was cleaned from hair, smoked and oiled. There were some vessels from 16 to 48 liters and from 50 to 150 liters. Kumis, which is made inside of simiir, differed with high taste qualities, had fizzy foamy consistency because of too much gas in it.
The quality of kumis depends on a leaven. Till the end of XIX century kumis was made mostly using leaven technology, which was made in the end of kumis season. Inside of simiir during summertime big cheesy precipitate, which is called hoyuu, that was dried and kept until springtime. This leaven was mixed in small quantity of new cow's milk, added some buttermilk and put dried horse tendon. If there was no last year leaven, they made a new one. For this cow's milk was soured with tar, sorat and buttermilk, as the result they received an iyejei. It was filtered, squeezed and put in small quantity of cow's milk, which was used as a leaven after the fermentation.