A line extended, and the square on 16 (Euclid II.8)
Line of 8+4 extended to 16; the square 256 divided into parallelograms
The folio is headed 'Eighth, [book] second,' citing Euclid's Elements. A line divided into 8 and 4 (whole 12) is extended by a further 4 to make 16, and the square on 16 (256) is drawn and divided into parallelograms. A column at the top left tallies the component areas 48, 48, 48, 48 and 64 to confirm the total of 256 arithmetically.
On this page
Line divided (8 and 4) then extended to 16
The line first divided into 8 and 4 (making 12) is drawn again 'extended,' with an added part giving 8 4 4 - 16. This extended line is the base of the following square.
The square on 16 equals 256, divided into parallelograms
The square on the whole extended line 16 is 256, drawn large and then divided into parallelograms. Smaller analogous squares repeat the construction below.
Column summing the parts to 256
A column at the top left adds the component areas 48, 48, 48, 48 and 64 to reach 256, with the paired figures 12/16 and 4/16 and 48/256. This confirms the area of the square arithmetically.
Citation of 'the eighth of the second'
The page names its authority, the eighth proposition of the second book of Euclid's Elements. The divided-and-extended line and its square 256 illustrate that proposition.