The Codex Atlanticus — the largest bound collection of Leonardo da Vinci’s writings — is moldy. So far the mold isn’t spreading, but the Biblioteca Ambrosiana in Milan doesn’t have the money even to analyze what needs to be done, nevermind actually do it.

Until more scientific analysis is done, the cause of the mold will remain unclear, said Cecilia Frosinini, the deputy director of the Opificio.

She said the mold could be the result of several factors, including exposure during any exhibition or study, or the unintended consequence of a restoration that began in 1968 and ended in 1972.

The Codex has some amazing engineering diagrams and inventions, including flying machines, swing bridges, pontoon bridges, covered bridges, trestle bridges, castles, pumps, water-powered saws, submarines, paddle boats, drills, canal excavators, canals, rotating cranes, mirror grinders, printing presses, weaponry galore and much, much more. The horizontal Tommy cannon is one my favorites: