While it is suggesting it was common at the time, it doesn't outright state they're talking about that time. At earlier points in history it certainly was acceptable, but we probably don't have pictures of it to go in textbooks. This reeks of them having a general point to make and having a picture that almost fits that point. I've made more tenuous connections for college papers before.
Also, while it's not as drastic, I was doing some looking into family history recently and I found some ancestors who got married around that time. The marriage certificate listed the wife as 17 and the husband as 21... but the math didn't add up when I found their birth certificates and on the marriage certificate she was aged up from 15 and he was aged down from 22. It was in a small farming community and at that point in time and place schooling was largely abandoned during harvest and as soon as kids were old enough to help out on the farm full time they would just stop with school. And for women, helping out on the farm meant taking care of the house and raising kids generally. Time at school was a waste for them so they just got right to the adult stuff immediately.
So I know this is a thread about toys, but it looks like you got a lot of good advice, and since you're new to cats, one thing that most people either don't realize or ignore is the number of litterboxes. 1 is not enough, even for a single cat. General rule of thumb for litterboxes is Number of cats + 1. You want them to view the entire place as their territory and a big part of that is scent markers. And the biggest of them is the litterbox. Many cats will, as soon as you change the litter, use it. That's because they want it to smell like their territory (To their sensitive noses). Spreading that around for them makes for a happy cat and reduces the chances of "accidents" or just marking territory later on in times of stress.
I'll also say you should probably have a scratching post on every room that they hang out in regularly. They're not going to go to another room to find it if they want a good stretch or scratch. I suggest angled or flat ones at first because they will often use them to really stretch out their spine so they need to get a lot of distance between stretched out back and front feet. That's a lot easier (and cheaper) in flat or angled ones. If they end up preferring upright ones they got to be real tall to give them what they want. And those are expensive.
One more tip. Even if you decide to feed them dry food, use designated feeding times. Read the package and figure out how much they should eat a day and split that in 2-3 parts and measure that out giving them meal times. It's better for their physical health and it's more in line with their body's natural rhythm.
In general though, it's best to establish routines for behaviors you want to promote (Cats love routine) early on and keep it up. If you try to introduce new routines later it's a lot harder to establish. The change of moving into a new home is the perfect time to create a new routine since everything is kinda chaos for them anyway and it helps them establish order in their lives.