“It is required that the vessel be not only round but egg-shaped.”
From Psychology and Alchemy:
“For the alchemists the vessel is something truly marvellous: a vas mirabile. Maria Prophetissa says that the whole secret lies in knowing about the Hermetic vessel. “Unum est vas” (the vessel is one) is emphasized again and again. It must be completely round, in imitation of the spherical cosmos, so that the influence of the stars may contribute to the success of the operation. It is a kind of matrix or uterus from which the filius philosophorum, the miraculous Stone, is to be born. Hence it is required that the vessel be not only round but egg-shaped.”
Collected Works 12, Paragraph 338
from The Alchemical Vessel as Symbol of the Soul, by Adam McLean
“The Retort in this archetypal case is a sealed flask. In this interior work we picture our soul as entirely sealed off from both the outer world and the universal spiritual realm. When we undertake this exercise we must have everything we need within the sphere of our inner retort, and for the duration of this work we are entirely self-contained and rely on inner change to take place within the components or forces we have within our being at that time. We have to work to bring about a transformation in these inner patterns, without relying on external forces. It is thus very important if we are to undertake such interior exercises in a positive way with any hope of any satisfactory results, to prepare ourselves and place in our inner retort all the energies and symbols that are necessary for the process. Thus working this particular exercise requires some degree of preparation.