Roots of Western Esotericism: Rosicrucianism 

Symbolized by the “Rose Cross”, Rosicrucianism is one of the earliest esoteric orders founded in Europe, around 17th century. Teachings of Rosicrucianism are a combination of Hermeticism, Christian Gnosticism and Qabalah. The order claims that its members possess secret wisdom that has its roots from ancient times and that secret wisdom includes a combination of alchemy and mysticism, which made Rosicrucians very influential among intellectuals and occultists back then. 

With the wave of Enlightenment in 18th century, Rosicrucianism lost its former glory to the skepticism and rationalism. However, allegedly most of its ideas and rituals stayed alive in Freemasonry in that century. After a century, new Rosicrucian orders appeared in Europe and the United States with some of them emerged out of Freemasonry.  There is a still visible influence of Rosicrucian philosophy and aesthetics on modern Freemasonry, and also some Hermetic orders see themselves as a successor of ancient Rosicrucianism.

The highly secret society practices astrology, alchemy with Egyptian and Greek mysticism and ritual practices like theurgy. To get a broad glimpse of their secret esoteric system, it is suggested to read the early manifestos “Fama Fraternitatis” and “Confessio Fraternitatis”. Early Rosicrucians were also heavily interested in literary, cultural, religious and scientific fields. Some modern groups suggest that the Rosicrucians have been active in these fields since the beginning of the Renaissance.

The early works of Rosicrucians include oblique passages referencing to their symbol Rose Cross, for example: 

"Thus Mr. Gall assured it would be so 

And my good genius doth surely know: 

For what we do presage is not in grosse 

For we be brethren of the Rosie Crosse; 

We have the Mason word, and second sight, 

Things for to come we can foretell aright."

— Henry Adamson, The Muses' Threnodie (Perth, 1638). 

How interesting to see a perfect blend of different philosophies and esoteric systems in one place, and to consider that it's an ancient knowledge. It's highly possible that no matter how much we research, we will still be at the tip of the iceberg of Rosicrucianism. However, that is what gives us a desire to research their rich corpus and learn more about their secret knowledge.