found on John Strype's
A SURVEY OF THE CITIES OF London and Westminster

Before we take our leave of Black Friers, I must mention a memorable Passage that happened after the Fire of London. Some Workmen digging in a Place there where the Covent was, to clear it from the Rubbish, by the appointment of Mr. William Bradford, in order to building; they came to an old Wall in a Cellar, of great thickness; where appeared a kind of Cupboard. Which being opened, there were found in it four Pots or Cases of fine Pewter, thick, with Covers of the same; and Rings fastened on the top, to take up or put down at pleasure. The Cases were flat before, and rounding behind. And in each of them were reposited four humane Heads, unconsumed, reserved, as it seems, by Art; with their Teeth and Hair, the Flesh of a tawny Colour, wrap'd up in black Silk, almost consumed. And a certain Substance, of a blackish Colour, crumbled into Dust, lying at the bottom of the Pots. Four Heads found in Black Friers.
J. S.
One of these Pots, with the Head in it, I saw in October, 1703. being in the Custody of Mr. Presbury, then Sope-maker in Smithfield. Which Pot had inscribed in the inside of the Cover, in a scrawling Character, (which might be used in the times of King Henry VIII.) J. CORNELIUS. This Head was without any Neck, having short red Hair upon it, thick, and that would not be pulled off; and yellow Hair upon the Temples; a little bald on the top (perhaps a Tonsure) the forepart of the Nose sunk, the Mouth gaping, ten sound Teeth, others had been plucked out; the Skin like tanned Leather, the Features of the Face visible. There was one Body found near it buried, and without an Head; but no other Bodies found. The other three Heads had some of the Necks joined to them, and had a broader and plainer Razure; which shewed them Priests. These three Heads are now dispersed. One was given to an Apothecary: Another was intrusted with the Parish Clerk; who it is thought got Money by shewing of it. It is probable they were at last privately procured, and conveyed abroad; and now become Holy Relicks.
Who these were, there is no Record, as I know of; nor had any of the Names inscribed but one. To me they seem to have been some zealous Priests or Friers, executed for Treason; whereof there were many in the Rebellion in Lincolnshire, An. 1538. or for denying the King's Supremacy. And here privately deposited by these Black Friers.

Sandra whose spectacled aura is positively astounded.