Figuarum Aegyptiorum Secretarum, 18th century.
The Holy Grail, symbol of the feminine sexual organs, contains the waters of life (sexual energy). Standing upon this water are the man and the woman, who use their staves (the Kundalini) to control the waters. The waters must be kept smooth and calm and absolutely pure, free from any defect or disturbance, for not a drop must be spilled.
From the tranquil and crystalline waters rises a column of stone, a symbol of the spinal column. The waters are the Foundation, which is Hebrew is Yesod, the Ninth Sephirah of the Kabbalah, and related directly to the sexual organs.
Upon the column are entwined the two serpents of the Caduceus, Ida and Pingala, known in Christianity as Adam and Eve.
Atop the column, supported by the work of the man and woman below, is the Innermost Spirit, our own Inner Divine Father and Mother, the Being. Unto the Innermost is given all glory and power, thus as the man and woman work to perfect themselves, the Innermost is given Initiations, powers, titles, grades, etc. This is why the Innermost is crowned and carries the Magic Wand and the Caduceus.
Surrounding all of this are Elohim who rule over the planets, whose force and influence direct and guide the couple in their Alchemical Work. All of the Gods carry within the force of the Cosmic Christ, whose symbol is the Sun; that is why all the wands, staves and sexual organs are covered by the Sun.
Compare this painting with the widely known symbol of the Shiva linga.