Definition of "pretious"

In pretious cloths his leg the chieftain ties, / Naught could the man from blood and fight debar.

1600, Edward Fairfax, The Jerusalem Delivered of Tasso, XI, lxxv

How vain therfore is it, and how preposterous in the Canon Law, to have made such carefull provision against the impediment of carnall performance, and to have had no care about the unconversing inability of mind, so defective to the purest and most sacred end of matrimony: and that the vessell of voluptuous enjoyment must be made good to him that has tak’n it upon trust without any caution, when as the mind from whence must flow the acts of peace and love, a far more pretious mixture then the quintessence of an excrement, though it be found never so deficient and unable to performe the best duty of marriage in a cheerfull and agreeable conversation, shall be thought good anough, how ever flat and melancholious it be, and must serve though to the eternall disturbance and languishing of him that complains him.

1643, John Milton, Doctrine and Discipline of Divorce