This manuscript dates back to the 13th century and is ascribed to Villard de Honnecourt, as “Album de dessins et croquis” ; it is currently not available as digitised copy .
On f. 3 one find, what so far is known to be the oldest occurrence, an illustration of a knight with a snail. The knight has a shield and a lance, but keeps both in rest with his left hand. With his right hand, he points at his forehead while looking at the snail. Nowadays we would think that he was saying “You are mad!”. However, was this also the intention of Villard de Honnecourt? Or was he simply bringing a salute to the snail?
This illustration has been copied many times, usually without comments. From one of these I learned “Here we see a study of an infantryman, armed with spear and shield. He also carries a club-like implement on his left arm, although it does not look terribly militaristic – more like an umbrella. His mail armor and (presumably) iron kettlehat identify him as a “middle-class” soldier, that is, not wealthy enough to own any plate armor, but wealthy enough to have an almost complete suit of mail. Note, too, the strap on leg armor and the well-drawn coif fastened about his chin.
Most interesting, though, is the additon of a note in 15th-century script that says, “De Honnecourt, he who went to Hungary.” It is possible, therefore, that this is a self-portrait and Villard fought in one of the 13th-century Hungarian wars, as some authors have so assumed. The late date of the script argues against this, and if it were the case, it is unlikely that there would be such a concentration on cathedrals (and religious images in general) and a singular lack of castles in the rest of the manuscript. For now, it seems, the enigmatic de Honnecourt who went to Hungary must remain a mystery.” .
The snail is stylised with a strongly segmented, dextral shell; the animal is shown with four tentacles and a humanised face with an eye. According to this site  it is suggested “”We see a snail-fish with horns (meaning occult forces, the mysterious cosmos)”. Any medievalist to comment on this?
 BNF, Ms. Français 19030, 33 ff.
 A fascimile has been published by Carl F. Barnes (2009): The Portfolio of Villard de Honnecourt. (Paris, Bibliothèque Nationale de France, MS Fr 19093). A new critical edition and color facsimile, Burlington.
 Principes de vie du voyageur. https://maykan.wordpress.com/2010/12/.