Enlarged diagram on f68v2-f68v1?

[Jorge_Stolfi]

Perhaps he was too focused on the upper "bumps" of this figure. However, he used a pair of compasses to draw a circle around a star.

He did use a compass with an ink attachment to draw most of the circles of the Zodiac and Cosmo, including the outlines of the islands in the Nine-Islands fold-out.  On many of them one can still see the pinprick at the center made by the pivot.

However, the circles often fail to close, and then the two ends run past each other, one mm or so apart, for a few cm.  Maybe those defects were caused by the vellum being floppy and wavy, or maybe his compass was not sturdy enough.  On the Beinecke scans, the traced circles also may deviate from round by one mm or so over several cm; either from the same causes, or because the vellum was not flat when imaged.

Some of the smaller circles -- like the "clock with hands" at the SW corner of the big fold-out -- probably were drawn freehand, or maybe by tracing around a template.  The almond shape at the center of the SW "island" may have been traced as two compass arcs, joined by freehand rounded points. 

He did use a straight edge on several Cosmo diagrams (but not, apparently, on the Nine-Things one).  However, he did not know how to divide a circle into equal parts -- not even 4 parts.  It seems certain that he had no set square, much less a protractor.

I haven't seen any trace of pencil sketches under the freehand drawings of lines that were supposed to be straight, such as the "logs" of f69v, the "cannons" protruding form  the central "island" of the big fold-out. or the baselines of radial text lines.  Maybe there were such sketches but they were erased or faded away.

All the best, --stolfi