I like the campfire idea. This can also be combined with the fireplace, though I'd say the fireplace is the indoors version.
When it comes to methods of saving that don't seem weird in-game, do remember that players tend to pay more attention to things that stand out rather than blend in. Especially when it comes to saving your game, it would be a bad idea to make it hard to figure out where to go for saving. Try to not make save points blend in to the point of being hard to find, though if you want to make your players hate you, you might want to do that.
As for concrete ideas about what to pick for objects: your setting will make a big difference in what kind of save points stand out like sore thumbs and which don't. Fireplaces would be hard to come by in modern towns with modern heating systems, for example. Post-apocalyptic, medieval and ancient cultures, however, would make at least campfires a good option.
Another way to save your game could be by using NPCs rather than objects. Instead of a book or hexagram, have e.g. an eccentric bard listen to your party's adventures or a wizard casting a spell. There's other ways to go about NPCs as save points for sure and they can be really interesting. You can also usually make them disappear from their fixed spots without it being weird - like if you're in a scene where you're being chased by an enemy and can't save, the explanation for the save NPC not being there could be that they are hiding from said enemy. In some other cases, saving NPCs are a worse choice, though - like in games where the protagonist is on their own and not sure if there are any people they can trust.
Just some food for thought, I hope it helps!