Umbra Recta.-->
Another maner of wyrking, by umbra recta-->:
Yif it so be that thou mayst nat come to the baas of the tour, in this
maner thou schalt werke. Set thy rewle upon 1 till thou see the
altitude, and set at thy foot a prikke. Than set thy rewle upon
2, and behold what is the differense between 1 and 2, and thou
shalt finde that it is 1. Than mete the space between two
prikkes, and that is the 12 partie of the altitude of the tour.
And yif ther were 2, it were the 6 partye; and yif ther were 3,
the 4 partye; et sic deinceps. And note, yif it were 5,
it were the 5 party of 12; and 7, 7 party of 12; and note, at the
altitude of thy conclusion, adde the stature of thyn heyghte to
thyn eye.
