I found very interesting to learn the source and the original meanings of Riccati’s Opere’s front-page. I think we should not, however, infer that the author meant to take the signified as well, together with the signifier.
Every aspect of our culture is deeply rooted in Judaism and in Christianity, and art is no exception. Note that for centuries “art” was mainly “holy art”. So, if in the XVIII century you are publishing your scientific work, and you are looking for a good metaphor or for a symbol, say, to represent the Enlightenment idea of “Light of knowledge triumphing over the darkness of ignorance”, you are likely to find good material or inspiration in the rich Christian art and iconography from previous centuries, that of course abounds of images of “X triumphing over Y”. The metaphor of “light vs darkness” itself is taken from the religious tradition, starting with the book of Genesis (Gen,1, 1-5), where it is used with other meanings. For instance, even the front-pages of (atheist) Diderot’s Encyclopaedia show religious images, or of clear religious source:
Taking an image from an old well established tradition does not imply keeping its symbolism: you are likely to choose an image because it is beautiful and fits nicely your needs (and yes, because it shows you are an educated person).