Itaque in quibuscumque locis horologia erunt describenda, eo loci sumenda est aequinoctialis umbra, et si erunt quemadmodum Romae gnomonis partes novem, umbrae octo, describatur in planitia et e media pros orthas erigatur ut sit ad normam quae dicitur gnomon.
Therefore in whatever places dials are to be set out, the length of the shadow at the equinox is to be taken. If, as at Rome, there are nine parts of the gnomon, and eight parts of the shadow, let a line be drawn on the level, and from the middle let there be set upright and with a set-square, a perpendicular which is called the gnomon;
final_alignments\Vitruvius_Architecture_Book_9.json