Dialogue

 1 Intro|       contained in planes, and plane rectilinear figures are
 2 Intro|      resting on a quadrangular plane surface, and composed of
 3 Intro|        solid angle out of four plane angles—six of these angles
 4 Timae|    kinds of mirrors, first the plane, secondly the concave; and
 5 Timae| contained in planes; and every plane rectilinear figure is composed
 6 Timae|        make out of every three plane angles one solid angle,
 7 Timae|  nearest to the most obtuse of plane angles; and out of the combination
 8 Timae|        solid angle out of four plane angles, and out of six such
 9 Timae|       of them included in five plane equilateral triangles, having
10 Timae|       the combination of three plane right angles; the figure
11 Timae| composed is a cube, having six plane quadrangular equilateral
12 Timae|      formed out of either, the plane equilateral quadrangle has