Ex qua parte lumen oporteat sumere, linea tendatur ab altitudine parietis, qui videtur obstare, ad eum locum, quo oporteat inmittere, et si ab ea linea in altitudinem cum prospiciatur, poterit spatium puri caeli amplum videre, in eo loco lumen erit sine inpeditione.
In the quarter from which light is required, a line should be drawn from the top of the party wall which seems to obstruct, to the point where light should be admitted. If the amount of open sky seems sufficient when we look up from that line, the light will not be obstructed.
final_alignments\Vitruvius_Architecture_Book_6.json