"The mercurial spirit - in both its Feminine and Masculine forms - is aware of the alchemist as he begins his opus.The alchemist’s insistence on keeping the alembic closed (and its content therefore private) encourages the patient to use the material in an appropriately introverted way and avoid betraying the integrity of the process either by recklessly acting it out or by fruitless theorizing."
The Philosopher on his journey investigating the Elements of nature is both like The Stranger who's apart from the group for a while and The Free Spirit who follows his intuition and imagination in pursuit of other horizons. The heron's house is closed, like the Philosopher's alembic, symbolizing a solitary introspection. He stays by the pine tree, which represents wisdom and longevity. At the same time the two horses in the Free Spirit would represent the mercurial aspect of the Philosopher with the masculine and feminine harmonized with music.
Note: the quote is from the book by J.L. Henderson and D.N. Sherwood, Transformation of the Psyche: The Symbolic Alchemy of the Splendor Solis