— FOLIO 74 (recto). —

Facsimile of Leonardo da Vinci's manuscript page, showing studies of a mechanical wing for a flying machine with annotations in mirror script. Below the facsimile is a printed transcription of the text.

Transcription of Leonardo's mirror writing from the facsimile:

A method so that when the wing rises high, it remains perforated original: "traforata"; this creates a valve effect to reduce air resistance during the upward motion, and when it descends, it is entirely solid; and the view of it is from the bottom up.

Drawing of a mechanical wing with components labeled A, B, and C.

— A B C — Make the meshes of this net 1/8 likely 1/8 of a "braccio," a Florentine unit of measure approximately 23 inches (58 cm). 1/8 would be about 3 inches wide. A shall be a shaft of fir wood that is "green" original: "inerbata," literally "in grass," referring to young, flexible wood, which is fibrous and lightweight. B shall be fustian fustian: a heavy, durable cloth made of cotton and flax with feathers glued to it, so that the air does not easily escape. C shall be starched taffeta a crisp, plain-woven silk fabric, and for a trial, you shall use thin papers.

— A method so that when the wing rises high, it remains perforated, and when it descends, it is entirely solid; and the view of it is from the bottom up.

— A B C —

— Make the meshes of this net 1/8 wide.

— A shall be a shaft of fir wood that is "green," which is fibrous and lightweight.

— B shall be fustian with feathers glued to it, so that the air does not easily escape.

— C shall be starched taffeta, and for a trial, you shall use thin papers.