How do old chess grandmasters (before computer era) practice their calculation/tactics?

I've been wondering what was their method when there were no online websites where you could just solve some tactics puzzles

...they solved physical tactics puzzles I guess. They are still a thing.

Perhaps Bobby Fischer was a prototype of his era. As a teenager in the 50s', he memorized thousands of GM games played by Russians. Fischer knew which bookstore in New York carried Russian chess journals.

Alekhine recommended solving mate in X problems.

I'm no expert but... maybe the current methodology of utilizing computer generated database positions in a random order is not efficient as a learning tool.

You don't have to go back that far to find somebody that learned without a computer... I learned when computers were weak - in an era when Jacob Aagard wrote an entire chapter on why computers would never be better than humans at chess. (which is hilarious to go back and read an older version of excelling at chess if you feel inclined). We all thought what he was penning though.

Probably this idea should be considered: The dean of chess, Arthur Bisguier, once told me that there was a time in his lifetime when you could read a single book on chess and know enough to be a chess master. I don't know for sure, (because I was a dumb kid that didn't ask questions), but I believe he was referring to the Bobby Fischer era in U.S. chess, when everyone played, but nobody had a great deal of information available - so relatively you could rise to the top of the pile with a single books worth of knowledge.

So.. the older methods? Memorizing games, but not memorizing like we think of it now -> more like building an understanding of each move and an idea of the logic that created it. Ask yourself why Irving Chernev was popular - the man that bridged this learning method to the beginner in the US.

Good luck!

I know they'd read magazines, books, periodicals in various languages, especially Russian. Fischer would do all that, as would everyone else who was a gm,etc I no there was something called the informant?? Which was a thicker periodical of endless columns of games played I assume all over the world .... Back when I was growing up, there'd be local chess clubs where guys would play. The clubs would often have their own little stapled together mailings w chess news, chess analysis, chess columns.... clubs were all over, every city had a few Now, online chess has killed almost all the clubs. There were a few chess books around back in the sixties, but not the multitudes available now.