Reading about historical beliefs about witchcraft and magic is no exception. On the other hand, if you expect to get notions for standard fantasy magic. . . .
It lends itself rather more to dark fantasy. Historical beliefs in magic-working have been relentlessly practical, and for obvious reasons, aimed at things you could not get by ordinary, lawful, and open means. Love magic and treasure hunting at best. Even fortune telling tends to have furtive and nasty aspects. Revenge gets a lot of play. With the death of children being popular. Also of beasts, which, in a time near to subsistence, could be as lethal. Drying up a cow's milk or keeping the butter from coming. On a larger scale, epidemics, arson, or shipwrecks. Sabbats were continually described as being places where they conjured up the terrible disaster of crop-ruining hail storms. And all this done safely far from any victim, so no one can know that you are responsible.
Not to mention the amount of stuff they used, and a lot of it is frankly nasty stuff. Even love magics -- omitting some of the ingredients found in some recipes, you have love magic poppets from ancient Greece where the figure is bound up and driven through with nails.
It conjures up a world tinged with a jaudiced yellow and a drab, flat black. (how the muse loves to play with colors for them. A red -- a brownish shade like dried blood. Orange like rust. A flat, dull, dark green, like the leaves you can see in a shadowy swamp. Blue and violet -- the muse had a little fun with those, for a bit claiming to have nothing -- but perhaps a bruise-like shade.)