Torquemada (Monarquia Indiana, Seville, 1615) says; (free translation) “They had, and still have, workmen who make knives of a certain black stone or flint, which it is a most wonderful and admirable thing to see them make out of the stone; and the ingenuity which invented this art is much to be praised.  They are made and got out of the stone (if one can explain it) in this manner.  One of these Indian workmen sits down upon the ground, and takes a piece of this black stone, which is like jet, and hard as flint, and is a stone which might be called precious, more beautiful and brilliant than alabaster or jasper, so much so that of it are made tablets[24] and mirrors.  The piece they take is about 8 inches long or rather more, and as thick as one’s leg or rather less, and cylindrical; they have a stick as large as the shaft of a lance, and 3 cubits or rather more in length; and at the end of it they fasten firmly another piece of wood, 8 inches long, to give more weight to this part; then, pressing their naked feet together, they hold the stone as with a pair of pincers or the vice of a carpenter’s bench.  They take the stick (which is cut off smooth at the end) with both hands, and set it well home against the edge of the front of the stone (y ponenlo avesar con el canto de la frente de la piedra) which also is cut smooth in that part; and then they press it against their breast, and with the force of the pressure there flies off a knife, with its point, and edge on each tide, as neatly as if one were to make them of a turnip with a sharp knife, or of iron in the fire.  Then they sharpen it on a stone, using a hone to give it a very fine edge; and in a very short time these workmen will make more than twenty knives in the aforesaid manner.  They come out of the same shape as our barbers’ lancets, except that they have a rib up the middle, and have a slight graceful curve towards the point.  They will cut and shave the hair the first time they are used, at the first cut nearly as well as a steel razor, but they lose their edge at the second cut; and so, to finish shaving one’s beard or hair, one after another has to be used; though indeed they are cheap, and spoiling them is of no consequence.  Many Spaniards, both regular and secular clergy, have been shaved with them, especially at the beginning of the colonization of these realms, when there was no such abundance as now of the necessary instruments, and people who gain their livelihood by practising this occupation.  But I conclude by saying that it is an admirable thing to see them made, and no small argument for the capacity of the men who found out such an invention.”