The diagram is not annotated. Maurice Davies has identified it as a version of one from Albrecht Dürer, Underweysung der Messung, Nuremberg 1525, perhaps through a secondary source;1 for most of the other notes in this sketchbook Turner probably consulted books at the British Museum (now held at the British Library, London), but Dürer’s is not listed there.
There is a related perspective lecture diagram (Tate D17135; Turner Bequest CXCV 164), which is comparatively elaborate, with many more superimposed sections through the body, suggesting Turner copied the original more accurately on another occasion. It was the first diagram for the first lecture; the second diagram shows a single section (Tate D17136; Turner Bequest CXCV 165). Another diagram derived from Dürer is on folio 3 verso (D07360).
Davies 1994, p.289.
There is slight offsetting from the ink heading and diagram opposite on folio 54 verso (D07450).