secrets are not the mea=nest, but next to the indagation of divine things, the principallprincipal and most - pretiousprecious of all, not to be investigated by circumforaneous impostors, and - pseudochymicallpseudochymical drones
Basically saying that the alchemical knowledge in this book will need to be deciphered and is hidden so that only those with alchemically knowledge can use it
So the Philosopher handles his subject, macerating, melting, dissolving, coagulating and fixing it in a pecu=liar water, which is stronger than the sharpest vinegar,
This appears to be a direct instruction of a alchemical process. Based off of previous text in the emblem, possibly for Mercury and Saturn
which by Geber is called white lead, who teachethteaches allsoalso, which way SaturneSaturn may by washing with Mercury be converted into Jupiter
This seems to be directly related to the epigram. More specifically where the epigrams states that "The livid Spots of Saturn's face correct, And make as white as Snow: when this is done." This seems to describe a process where Mercury is transformed through a process with some element related to Saturn