Nowadays you’d load up your Kindle or whatever. It used to be harder as we all remember. President Teddy Roosevelt’s, no doubt a big traveller, didn’t want to be caught short. Crusoe’s Books has a post about his traveling library, which included the following:

Obviously quite a serious reader. George Borrow matches Sir Walter Scott with the top title count. Not much read these days, George Borrow (Sir Walter either, I guess). I did read Lavengro 20 years ago, and there is a sort of fascination with all that gypsy lingo stuff.

Traveling libraries are clearly a bit of a preoccupation of theirs at Crusoe’s Books — here’s another post on the subject, featuring the collections of the young King Charles 1 and Napoleon as well as William Hakewell. I guess a precondition for having a traveling library is having stalwarts to lug it around for you. And of course money enough to pay them and also to get your books uniformly leather bound as they all seem to be. King Charles’ are the most impressive. (Presumably the polystyrene spacers are not original!)

The king’s books are mercifully small: