The story goes that sometime between 1370 and 1382, during their annual procession of a fragment of the Holy Cross, members of the elite Scuola di San Giovanni Evangelistra somehow dropped the relic into the canal while crossing over the Ponte di San Lorenzo in front of the eponymous church. Panic ensued, and a number of men dived for it, but only the confraternity's leader, the Gran Guardiano Andrea Vendramin, was able to retrieve it.
It was hardly the highest-octane miracle of all time, but good enough to feature among the series of nine canvases on the Miracles of the Holy Cross, commissioned by the wealthy scuole from some of the greatest artists of the 15th century. Most now hang in the Accademia, including Gentile Bellini's meticulous painting, with the robed Gran Guardiano floating in the water like a ghostly merman. The woman standing and praying on the far left in the dark dress is said to be Catherine Cornaro, while portraits of Gentile and his brother Giovanni Bellini number among the worshippers on the right.
Images by Axbay, Creative Commons License, PD Art