Yes but the fact is, they did put all these mystical meanings onto the numbers, as part of their interest in astrology and numerology and so forth. It was part of the education most people got back then. It doesn't mean it wasn't also prosaic, but they tended to group things together by what they saw as their innate characteristics of certain numbers.

So they tended to see 3 as associated with the trinity and 1 with the sun and 5 with the rose (and therefore noble or lucky) and 8 with Saturn and therefore bad luck and so forth.

This was strongly linked to both weapon design and fencing, as we know the fencing master Talhoffer included one of the earliest European astrological discursions in his 1459 fencing manual, nor was he by any means the last.

Sol was associated with fencers while mars was associated with robbers, killers and warfare. War was looked upon as evil but martial skill as a good. You can see the concepts displayed clearly in these plates from the Schloss Wolfegg Hausbuch



Sol (note the fencers in the top of the plate)


Mars (note the death and mayhem of a village raid)

How literally they believed all that stuff is an entirely different question. I suspect from what I have read, in most cases - not very. Their sources for these ideas were from ancient Greek, Hebrew, Arabic, Persian (and so forth) sources, whose theology they didn't necessary adhere to. But they saw the patterns did exist and were useful. I think part of understanding the medieval mind is that they tended to carry around a lot of 'provisional' ideas in their heads.

But while they may not have believed literally that the astrological nature of the salt of saint peter, brimstone, and charcoal combined in such a way as to make fire, they did know that following the pattern gave them gunpowder. And gunpowder go bang.

Similarly, they knew certain mystical patterns, which they could assign to Sol or Venus or Luna or whomever, allowed them to put together very nice swords. As HP Lovecraft said, you don't have to believe in Santa Claus to get Christmas presents on Dec 25.

G