Max distance player can jump foreward = 244
Max distance player can jump upwards = 43
Max distance player can fall not injured = 256
Min gap in floor before fall through = 33
Max step player walks before jumping = 18
And yes, those are for Netquake, id1, vanilla, etc.
Also note that, I believe, there's a slight difference between old SW Quake and source ports concerning the out-of-water height (29).
yeah, the out-of-water height is a bit sensitive. Not everyone can get out of water when the ledge is 32 units high! Make it 16 to be safe.
Following What Gb Said...
in general try not to build anything to the exact maximum, if you want the player to succeed. Because physics is framerate dependent, some players might not be able to make a jump that is theoretically possible.
Also geometry built near the threshold between "can" and "can't" is ambiguous to the player and makes the environment harder to read. For example you want gaps that are obviously "jumpable" or "unjumpable" when a player looks at them. (exception may be in DM maps where expert players are supposed to be challenged to learn the quirks of the map.)
For example, 16 units is a good max step height. 32 is a good minimum non-step height. 40 units is a good max jumpable height, 48 is a good minimum for un-jumpable height.