The ranking can be seen here Pitcher’s Homerun/Walk Rating. In the Bill James Goldmine book he has a section on ranking pitchers just on HRs and walks. I did something like that once. Here is the basic idea:
The ranking at the link above was generated using the Lee Sinins Complete Baseball encyclopedia. It includes all pitchers from 1920-2006 with 2000+ IP. There were 277 pitchers. REL BB means relative walks. For Eppa Rixey below, the 1.455 means that the average pitcher walked 45.5% more batters per 9 IP than he did in his career (2.78 vs. 1.91). REL HR means relative HRs. The 2.013 for Rixey means that average pitcher allowed 101.3% more HRs than he did (155 vs. 77). If a pitcher has a number below 1, he was worse than the average pitcher.
HR*BB is just the previous 2 multiplied by each other. Greg Maddux ranks very high. Only Rixey is ahead of him. But he pitched almost all of his post 1920 time with the Reds (1920 with Philadelphia and 1921-33 with the Reds). Their park was extremely difficult to hit HRs in. From 1920-29, it allowed only 22% as many HRs as the average park in the NL! (that is according to the STATS, INC. All-Time BASEBALL SOURCEBOOK) That helps explain why Rixey does so well. The only other pitcher besides Maddux to have a score of 1.50 or more for both HRs and BBs is Pete Donohue. But Donohue also spent almost all of his career (which lasted from 1921-32) with the Reds. So, for all practical purposes, Maddux is the only pitcher to best the league average by at least 50% in both HRs and BBs! I think it is amazing that a guy who put the ball in the strike zone so much would give up so few HRs.
Maddux allowed 318 HRs while the average guy allowed 483 (483/318 = 1.519). He walked 1.84 per 9 IP while the average walked 3.34 (so 3.34/1.84 = 1.815).