vigesimal แปลว่า

"If the years of the incomplete century be divided into twenties, and the excess of twenties resolved into fours, the Dominical Letter will advance three places for every twenty, two places for every four, and six places for every unit of the still outstanding remainder. Hence the Sunday Letter will be found by taking the sum of four numbers, which may be called the centurial, the vigesimal, the quaternial, and the residual."

"[column 1] The author of this article has also designed an instrumental contrivance for finding Easter by inspection, for any year from the beginning of the Christian era down to the end of hundredth century, in old style or new. […] [column 2] Around the fixed ring here described is a rotary ring bearing the numbers from 1 to 19 (the golden numbers) twice repeated, and at the left of these the vigesimals, arranged in regular order."

"They had all attended an abacus school (scuola d'abaco), where the basic training program, well known from the numerous practical treatises on the subject that survive, had taught them above all how to deal in different moneys and to make the four basic arithmetic calculations, using what for them was the standard mensural system based on vigesimals and duodecimals."