Carl Jung says that “the mother image “can be attached to … various vessels.” [1]

There is a relation between the alchemical vessel and the concepts of prima materia. Materia prima is the formless base of matter. In both Vedic and Biblical traditions, this primal matter is related to the mother principle. In Genesis, God hovers over the deep: “And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.”  In the Rig Vedas, the waters are synonymous with the mother: “May the waters (ap), mothers (matr) purify us” (10.17.10)

In alchemy, the vessel offers an imaginal space for transformation. The alchemist used vessels to carry out their alchemical operations. It was in such vessels that distillation and transformation occurred, making them a suitable image for the transformation and distillation of spiritual energies.

The image above shows an alchemical vessel and on it is an Ouroboros. The image is found in Aurora consurgens from the 15th Century. The ouroborus takes the form of a dragon in this alchemical drawing. Jung notes the relationship of the ouroboros to alchemy and the prima materia:

The alchemists, who in their own way knew more about the nature of the individuation process than we moderns do, expressed this paradox through the symbol of the Ouroboros, the snake that eats its own tail. The Ouroboros has been said to have a meaning of infinity or wholeness. In the age-old image of the Ouroboros lies the thought of devouring oneself and turning oneself into a circulatory process, for it was clear to the more astute alchemists that the prima materia of the art was man himself. The Ouroboros is a dramatic symbol for the integration and assimilation of the opposite, i.e. of the shadow. This ‘feed-back’ process is at the same time a symbol of immortality, since it is said of the Ouroboros that he slays himself and brings himself to life, fertilizes himself and gives birth to himself. He symbolizes the One, who proceeds from the clash of opposites, and he therefore constitutes the secret of the prima materia which […] unquestionably stems from man’s unconscious. (CW 14, para 513)

The Image shows the relation between the vessel and the Ouroboros (as predawn state).  Erich Neumann believed that the Ouroborus image expressed a pre-ego or “dawn state” state of psychic life. This state is the natural undifferentiated awareness of the human being. This state of awareness is there in the pre-ego state of the infant, as well as in the “pre-dawn” state of mankind.

References:

1. The Archetypes and The Collective Unconscious (Collected Works of C.G. Jung Vol.9 Part 1)  157
2. The Face of the Deep: A Theology of Becoming by Catherine Keller
3. Mysterium Coniunctionis by Carl Jung 
4. The Origins and History of Consciousness by Erich Neumann
   
5. Aurora and dragon. Aurora Consurgens-15th Us Public Domain

Reference:

Thomas Aquinas; Marie-Louise von Franz (1966) Aurora Consurgens; A Document Attributed to Thomas Aquinas on the Problem of Opposites in Alchemy, London: Routledge & K. Paul century.