Appleton's cyclopaedia of drawing : designed as a text-book for the mechanic, architect, engineer, and surveyor : comprising geometrical projection, mechanical, architectural, and topographical drawing, perspective and isometry (1869)
Worthen, W. E. (William Ezra), 1819-1897 · New York : D. Appleton and Company · leaf 612
at its intersection by m S. Connect the points hvs m, and also their projected perspective points li Y s' m', and we find that when an original line is parallel or perpendic- ular to the base of the picture, the perspective of that line will also be par- allel or perpendicular to it. Fig 5. Draw… … Fig. 5. the plane of the picture, the line m' M must be the projection of this line on the plane of the picture, and if this line be extended it will pass through Y, which may be demonstrated of all lines perpendicular to the plane of the picture ; hence the perspective direction of lines…
