Originally Posted by due ruote

This makes sense to me. The only way to have it right is to ride and adjust, incrementally, until you find the sweet spot. I would define that as the nose low enough that you don't get numbness, but high enough that you don't slide forward, which is fatiguing on the arms and shoulders. The angle will vary depending on the type of saddle (this should be obvious).
If I ever tear a bike down or remove the saddle for any reason, I take a scrap stick of wood and hold it vertically against the top tube, and make a mark for the saddle nose. If the stick is long enough, do the same thing for a measurement from stem to saddle nose. This way you can quickly get the saddle back to a position that likely took some time and effort to arrive at in the first instance.