Back in the old days, "something for the weekend" was a coded phrase for condoms (when barbers' shops used to sell such things, the hairdresser would finish scalping you and then ask "would you like a little something for the weekend, sir?"). Musgraves was a chemist/herbalist where a likely lad could buy such things (or so I'm told.
). Obviously, the phrase has fallen into disuse these days, now you can just pick them up on the shelves of any supermarket.