What's the oldest p4p list that we know of?

Probably some dude from 1720

 

Still a list tho ain't it?

I have seen a few P4P lists of fighters from the 1880s and onwards, but not really prior to that. I know there were comparisons between eras though, example would be how Mendoza era fighters saw themselves as more technically advanced than Broughton era fighters. I'm sure they had lists back then, but it would take quite a bit of digging to find it.

 

It's a modern fad.
I haven't seen any p4p list prior to 1980s, KO magazine. I don't remember it being a major promotional device until a few years ago.

 

This isn't exactly what you asked for, but in 1917 Grantland Rice called Bob Fitzsimmons the greatest pound for pound fighter of all time, ahead of his contemporaries Joe Gans and Terry McGovern.

https://ibb.co/BYWvZGs

 

Achilles
Hector
Duran
Spartacus
Alexander
Boudicca
Robinson
Leonidas
Pai Mei
Pep

 

Wasn’t the term P4P originally created by sports journalists as a way to compare boxers across different weight classes, essentially emerging from Sugar Ray Robinson’s dominance? In the sense of: “Regardless of the weight class, he would be the best,” if there were no physical limitations…

In that sense, it wouldn’t be that old at all. According to Boxrec, the first official Ring Magazine P4P rating (annual) only appeared a few decades later.
1989:

1. Mike Tyson

2. Julio Cesar Chavez

3. Pernell Whitaker

4. Michael Nunn

5. Antonio Esparragoza

6. Meldrick Taylor

7. Azumah Nelson

8. Raul Perez

9. Virgil Hill

10. Marlon Starling

Obviously, rankings within individual weight classes are much older, since you need a system to compare fighters or potential contenders with each other.
Of course, individual comparative statements, even across weight classes, can go back much further as well…

 

The term pre-dates SRR. I've seen it applied to boxers in 1920s, maybe 1910s.
It just means "pound for pound". Like a pound of gold is worth more than a pound of flour, a pound of Sam Langford is worth more than a pound of Jess Willard. That's all it means.

It was usually applied to boxers such as Sam Langford, Joe Walcott, Mickey Walker, etc., who competed with and beat men who were much heavier.

 

"Pound for pound" rankings lists, however, and especially the idea that the lists are IMPORTANT, is a very recent fad.