First, his work was heavily centered on frescos (that is, wall paintings created in wet plaster), which generally must be viewed on-site and are often located in places of restricted accessibility.
"[6] The early 20th century brought the further discovery that Bortoloni had flexibly based his imagery at Villa Cornaro-Gable in large part upon an illustrated Bible published in Amsterdam in 1700, apparently in response to the requirement of the patron, Proc.
[9] Ernesto Billò, Santuario Basilica della Natività di Maria Regina Montis Regalis, Vicoforte (Gorle: Editrice Velar, 2012).
Nicola Ivanoff, "Mattia Bortoloni e gli Affreschi Ignoti della Villa Cornaro a Piombino Dese," Arte Veneta, vol.
Douglas Lewis, "Freemasonic Imagery in a Venetian Fresco Cycle of 1716," in Hermeticism and the Renaissance: Intellectual History and the Occult in Early Modern Europe, edited by Ingrid Merkel and Allen G. Debus, (Washington, D. C.: The Folger Shakespeare Library, 1988), pp. 366–399.