Étienne Guibourg

Montague Summers gives an account of one such ritual:[2] A long black velvet pall was spread over the altar, and upon this the royal mistress laid herself in a state of perfect nudity.

Six black candles were lit, the celebrant robed himself in a chasuble embroidered with esoteric characters wrought in silver, the gold paten and chalice were placed upon the naked belly of the living altar [...] All was silent save for the low monotonous murmur of the blasphemous liturgy [...] An assistant crept forward bearing an infant in her arms.

The child was held over the altar, a sharp gash across the neck, a stifled cry, and warm drops fell into the chalice and streamed upon the white figure beneath.

The corpse was handed to la Voisin, who flung it callously into an oven fashioned for that purpose which glowed white-hot in its fierceness.Summers provides a further account of the incantation used by Guibourg himself:[2] Astaroth, Asmodeus, princes of friendship and love, I invoke you to accept the sacrifice, this child that I offer you, for the things I ask of you.

[2] Eleanor Herman, in her book Sex with Kings, claims that the police, given reports of "babies' bones", uncovered the remains of 2,500 infants in La Voisin's garden.

Guibourg performing his Black Mass with the naked body of Madame de Montespan for an altar, as depicted in The Guibourg Mass by Henry de Malvost, Paris, 1903.