Hieronymus Cardanus De Subtilitate puts on display an intriguing short for the number seven. A Cardanus trick, or a lost symbolism?

Sometimes serpents and snakes seem to be used out of contest in alchemical symbolism. I just notice that sometimes serpents are redundant in hermetic pictures. Especially when they over repeat other symbols already standing for our three principles. What about their meaning as the number seven, so often just alluded in symbolism due to the great importance this number has?

Cardanus was chiefly known as the inventor of Cardan Joint. Son of a Leonardo da Vinci close friend, was a polyhedric mind himself. Physician and mathematician, an italian renaissance scientist for antonomasia.

I was running over Cardanus De Subtilitate, Basel 1560, searching for cardan joint when I stumbled upon this intriguing image on page 472. Cardanus is here describing a device by Ianellus as an inspirational forerunner for his joint.  He says that the device with seven gears was called, for this reason, SERPENS, as serpens had seven letters.

“His lineis septem dictionis literae…….septem literarum sit SERPENS……..”

Serpens is the latin for serpent. And seven repetitions of the same process is often the missing, and forbidden,  information in alchemical proceedings. Since these repetitions represent often the no man land between ancient chemistry and Alchemy.

Was it a common knowledge in renaissance time? Or just a Cardanus amusement?