V.I.T.R.I.O.L. is an acronym which stands for Visita Interiora Terrae Rectificando Invenies Occultum Lapidem. This translates to "Visit the interior of the Earth and by rectification (purification) you will find the hidden stone." This image is purportedly found on the Emerald Tablet of Hermes (Tabula Smaragdina Hermetis) and is a revered alchemical text of the Rosicrucian order.
According to legend, Christian Rosenkreutz was the founder of the Rosicrucian order who discovered and learned Esoteric Wisdom among Arab sages as a pilgrim to the East, supposedly in the early 15th century. He returned and founded the "Fraternity of the Rose Cross" with himself (Frater C.R.C.) as head of the order. Under his direction, a temple, called Sanctus Spiritus, or "The House of the Holy Spirit", was built.
It is described that his body was discovered by a brother of the order, in a perfect state of conservation, 120 years after his death (which occurred in absolute secrecy) — as Rosenkreuz had predicted — in a chamber erected by himself as a storehouse of knowledge.
We cannot discount the secrets of these holy orders and how the greatest secret of them all is the truth of the inner earth, concealed for centuries right up to this very day!