Sentence:  The most remarkable <WSD>vigesimal</WSD> scale of numeration is that of the Mexicans. The decimal scale is adopted as far as twenty; that is to say, after ten the primitive digits are repeated, but from twenty onwards the numbers are taken by twenties. Thus 34 is "canlahhutukal", literally fourteen and twenty. 
Meaning of the word marked with <WSD> tags:  To the base twenty. (from mid-17th c.)