De Religione Catharon

Maurice Magre was a French author from Toulouse, a contemporary of H. Spencer Lewis and a fellow student of mysticism. Magre held a romantic view of the history of his native Languedoc and the persecution of medieval Cathars in that region.

He developed a notion that C.R.C. was a scion of a Cathar family, and that he and his earliest Rosicrucian brethren were educated in that religion, but this seems a little far-fetched to me.

The Cathars held a dualistic view of creation, and thought renunciation was essential to escape the hateful material plane once and for all. This is a far cry from elevating nature almost to the status of co-redeemer as the Rosicrucians did.

The Cathars may have interpreted Christian resurrection as a kind of repetitive reincarnation, with final escape from material existence only being possible once the soul has reached a certain level of maturity over multiple lifetimes, and that's not dissimilar per se to some Rosicrucian teachings and those of other spiritual movements. But a vague similarity doesn't establish a plausible link.

For the Cathars, nature was not a divine classroom but an infernal prison, and the Rosicrucian manifestos just don't share that same general outlook.