For all that the 1800s etiquette guides are--obviously--derangedly sexist from a modern perspective? They're also mindblowing in how casually they will assert things that MODERN DAY CONSERVATIVES would scream and cry and shit their pants about.
"People back then always married young it's natural!!!" Every single 1800s guide I've ever met casually mentions that, of course, you really shouldn't get married before you're at least 20, and waiting until 25 is usually better.
Or, like. Okay here's a long segment:
Just firmly going "it is crazy sexist to blame The Wife for overspending when thirty seconds of asking questions will immediately establish that her husband was outright lying to her about how much money they had. Talk to your wife like a normal person."
Or--okay, here. A section on being honest and not writing love letters in secret, because that's usually a good sign that there's something untoward going on....
....except that he then immediately acknowledges that sometimes, the reason you're hiding this from your parents is that your parents suck. That there are parents who frankly have not earned the right to approve or disapprove of your partner.
(I realize the phrasing there sounds a lot less strong than my summary, but--trust me on this. When you're familiar with the narrative voice of these kinds of books, this passage is downright radical. The mere acknowledgement that if you treat your kids badly, it's your own damn fault when they don't talk to you? I've genuinely never seen that before in this genre.
Don't freak out over "properly trained", either. It's just a linguistic shift--at the time, "training" was used the way we would say "raising" a child today. )