The flywheel as a general mechanical device for equalizing the speed of rotation is, according to the American medievalist Lynn White, recorded in the De diversibus artibus (On various arts) of the German artisan Theophilus Presbyter (ca. 1070–1125) who records applying the device in several of his machines.
A medieval guide to gem-carving techniques survives from Theophilus Presbyter.
Theophilus | Theophilus Presbyter | Theophilus Parsons | Theophilus Waldmeier | Theophilus Shepstone | Theophilus Howard, 2nd Earl of Suffolk | Theophilus Cibber | Theophilus Cazenove | Theophilus Pinches | Theophilus Oglethorpe | Theophilus Hastings, 7th Earl of Huntingdon | Theophilus Danzy | Theophilus Adam Wylie | John Theophilus Desaguliers | William Theophilus Dortch | Theophilus Weeks | Theophilus Van Kannel | Theophilus of Adana | Theophilus Hastings, 9th Earl of Huntingdon | Theophilus (emperor) | Theophilus Eaton | Theophilus Danjuma | Theophilus Browne | Presbyter Judaeorum | Henry Theophilus Finck | Harry Theophilus Toulmin |
He prepared a new edition of the monk Theophilus' celebrated treatise, Diversarum artium schedula, and for several years devoted his Saturday mornings to laboratory research with the chemist Aimé Girard at the Conservatoire des Arts et Métiers, the results of which were utilized by Marcellin Berthelot in the first volume (1894) of his Chimie au moyen âge.
His discussion of oil painting was important for dispelling the myth, propagated by Giorgio Vasari and Karel Van Mander, that oil painting was invented by Jan van Eyck (although Theophilus (Roger of Helmerhausen) clearly gives instructions for oil-based painting in his treatise, On Divers Arts, written in 1125).
However, Theophilus (Roger of Helmarshausen?) clearly gives instructions for oil-based painting in his treatise, On Various Arts, written in 1125.