House cusps in mundane astrology

1
I was reading Raphael (the 3rd) last night on mundane astrology and he mentioned house cusps. He described a formula that I haven't seen anywhere else before. What he said was to take the number of degrees between one house cusp and the next and then divide this by three. This one third then becomes the house cusp. So, for example, if the cusp of the 12th house is 13 degrees Aquarius and the 1st cusp is 0 degrees Aries there is 47 degrees between house cusps. Divide this by three and we get almost 16 degrees. So if a planet in the 12th house is within 16 degrees of the ascendant it is deemed to be in the 1st house. This seems quite excessive to me. But what I want to know is whether there is a precedent for this, i.e. has anyone before Raphael said something similar or is this something he devised on his own reckoning?

2
I?ve never seen this before. So are you saying he only advises this for mundane astrology and not natal astrology, etc? It does seem excessive but it may have a precedent in some earlier work given that Bonatus has been mentioned a few times for explaining alternative views on deriving house cusps (15 degree cusps have been mentioned, plus a graduated cusp depending on angularity, so there may also have been attempts to vary the cusp according to the size of the house). From what Kim Farnell was saying, the Raphael?s were unlikely to be ?innovating? techniques, so I would imagine he must have taken this from some older text.

I?m going to place a copy of your post in the ?planets close to house cusps? thread in the nativities section, because it might make a useful reference for anyone researching their use throughout history. Can you give the reference for it?

3
So are you saying he only advises this for mundane astrology and not natal astrology, etc?
The book is specifically about mundane astrology but he clearly states that he is talking about mundane house cusps.

It is 'Raphael's Mundane Astrology' and is reprinted by Astrology Classics Publishing. It is part of a trilogy that also includes H.S. Green and C.E.O. Carter. I would imagine there are several other versions of the reprint available.