transtemporal
Explorer
Thanks for all the sick and twisted replies guys!
Well if you're dead set on using only mundane resources, you'll be hard pressed to keep even a medium level wizard contained.
You can't in 1e either.
Nice solution: put him in heavy armor. No spellcasting without proficiency. (Do this on top of manacles + gag just in case he really does have proficiency anyway.)
This is about guards restraining your caster PCs, right? But how helpless do you want them to actually be though? I mean, if you just keep them completely immobilized with zero options then your players might not have a good time. If you're looking for an in-universe explanation for why the city guard would be unprepared, it could just be that non-spell magic abilities like some of the work arounds that arcane traditions provide or options like subtle spell are not things that most casters of the setting have; Player characters are special after all. Sorry if this wasn't helpful, just tossing a few thoughts out there.