nauhtzontli.

4 x 400, or 1,600; four times one tzontli (where a tzontli is 400)

(eighteenth century; used by a doctor who was not a native speaker but had studied classical Nahuatl)
Neville Stiles, Jeff Burnham, James Nauman, "Los concejos médicos del Dr. Bartolache sobre las pastillas de fierro: Un documento colonial en el náhuatl del siglo XVIII," Estudios de Cultural Náhuatl 19 (1989), 269–287, see p. 284.