Eight Latin couplets once inscribed in the octagonal baptistery beside Milan cathedral, recorded in a medieval collection and generally attributed to Bishop Ambrose. They explain why the font and its building have eight sides.
Ambrose, bishop of Milan from 374 to 397, built churches round his city and baptised Augustine there at Easter 387. The poem survives in a ninth-century sylloge (a collection of inscriptions copied by travellers), which records it as written at the baptistery of Santa Tecla. Excavation under the cathedral square found an octagonal baptistery with an octagonal font, San Giovanni alle Fonti, that fits the description.
The poem argues from numbers: the temple has eight niches and the font eight sides because the eighth day (the day after the seventh, on which Christ rose) is the day of salvation, and baptism is dying and rising with him. The reasoning was repeated for a thousand years, and the octagonal baptistery became a type from Ravenna to Florence.
The book, part by part
I The epigram
Eight niches, an eight-sided font: the number of the resurrection.