From Splendor Solis:
Eighthly: When the Sun is in Aries, he indicates the First Heat, or Grade of the Fire,
which is weak because the heat is under the Rule of the Water,
but when the Sun is in Leo, then it indicates the Second Grade,
which is hotter because of the great coldness of the Water being under the Rule of the Air.
In the Sign of Sagittarius is the Third Grade, this being not a burning heat,
and under the Rule or Order of Rest and Pause.
Aries is the diurnal sign of Mars. Aries, a Fire sign, represents drives (such as flight or fight). Herakles learned to control his drives by choosing a life of Virtue and purified his Dense (Material) Body (and Conscious Soul).
Leo is the sign of the Sun. Leo is also a Fire sign. By learning to control his passions, Herakles purified his Vital (Etheric) Body and his Intellectual Soul.
Scorpio is the nocturnal (feminine) sign of Mars. Scorpio, a Water sign, represents emotions. By learning to control her emotions, Psyche purified her Desire (Astral) Body and her Emotional Soul.
Sagittarius is the diurnal sign of Jupiter. Sagittarius is a Fire sign, but Jupiter, a Lord of Mind, is associated with Air.
“The Spirit dissolves the body, and
in the Dissolution extracts the Soul of the Body, and
changes this body into Soul, and the Soul is changed into Spirit, and
the Spirit is added again to the Body, for thus it has stability.”
The Spirit dissolves Herakles’ Dense (Material) Body and in the Dissolution extracts the Conscious Soul (so Herakles crossed the Veil of Ignorance). This is the Grade of Fire, the First Alchemical Marriage.
The Spirit dissolves Herakles’ Vital (Etheric) Body and in the Dissolution extracts the Intellectual Soul. The Spirit dissolves Psyches’ Desire (Astral) Body and in the Dissolution extracts the Emotional Soul. The Conscious Soul, the Intellectual Soul, and the Emotional Soul are changed into Spirit, and this Spirit is added again to the Body, for thus it has stability.
The Conjunction of the Conscious Soul, the Intellectual Soul, and the Emotional Soul allows Herakles and Psyche (Will and Imagination) as a unified and purified Soul to cross the Veil of Illusion. This is the Grade of Water, the Second Alchemical Marriage.
The Sign of Sagittarius, the Grade of Air, refers to the next set of Plates.