Forgive me for the silly question but I'm rather unfamiliar with how copyright works in this case. I'm considering on doing a retelling of an old myth in comic form but it is rather strongly based off from a so called 'compiled official' source dated back to 1800. There's no publication intended for what I'm doing, but more for practice sake and possibly sharing over webcomic websites. However, I would like to do this right and understand how far I can go with this. I have no intention of stealing, I definitely intended to reference the original source. I'm just curious if what I'm doing is illegal, if this piece of work is based off a source dated that long ago?