What is "matracas"

Usage examples of "matracas".

They were led by a pitero piping a reed and then in procession a clanging of tambourines and matracas and men naked to the waist in black capes and hoods who flailed them­selves with whips of braided yucca and men who bore on their naked backs great loads of cholla and a man tied to a rope who was pulled this way and that by his companions and a hooded man in a white robe who bore a heavy wooden cross on his shoulders.