"THE Pearl has this Prerogative above all other Jewels, that whereas they require form and lustre from Art, the Pearl only is perfected by Nature. Its colour, roundness, smoothness and bigness (in which consists its whole beauty) are all fram'd in its Mothers womb; but Man is a Jewel of another Nature; like the Diamond though he brings his perfection from the Bed, nevertheless 'tis rough and unpolish'd: much pains and Art must be us'd for the fashioning; and the more great and excellent the Stone, the more labour and diligence is requir'd for the polishing, and indeed maugre all the Art and care of the Workman, some Diamonds can never have their flaws conceal'd or mended by the help of any foil whatever."
— Nourse, Timothy (c.1636–1699)
See Timothy Nourse, A Discourse Upon the Nature and Faculties of Man in Several Essayes With Some Considerations of Humane Life (London: Printed for Jacob Tonson at the Judge’s Head in Chancery-Lane, near Fleet-street, 1686). <Link to ESTC><Link to EEBO-TCP>