La Crypte du piédestal de la Lampe Sépulcrale - ("The Crypt of the pedestal of the Sepulchral Lamp")
The pedestal of the sepulchral lamp owed its origin to the necessity of obtaining a more free circulation of air in the catacombs. This induced the workmen to place a large vessel with fire on a block of stone; and the appearance of this suggested the idea of substituting a sepulchral lamp in its place. The lamp is in the form of an antique cup, and was the first monument erected in the catacombs.
(ref: "The Modern Voyager & Traveller Through Europe, Asia, Africa, & America: Europe" By William Adams (M.A.))