Here is the poem Erasmus ... yes; more fruits of my afternoon in Bodley with the Merton Priory copy of Erasmus ... composed to go with a picture of the Child Jesus which his fellow Humanist Dean Colet had put up in the school he founded and headed at S Paul's Cathedral in London.
Sedes haec puero sacra est Iesu
Formandis pueris dicata; quare
Edico, procul hinc facessat, aut qui
Spurcis moribus, aut inerudita
Ludum hunc inquinet eruditione.
It is written, as you perceive, in Phalaecian hendecasyllables. Quaerendum: Did Erasmus derive the use of this metre from Catullus, or from Martial? The former survived antiquity only in the Veronensian codex discovered in the middle of the fourteenth century, while Martial was much more widely known at least from the Carolingian Renaissance onwards. I think I can prove it was Martial: there is a lovely little book in the British Library containing verses by the Italian Humanist Giovanni Gigli (1434-1498), later bishop of Worcester, but, when he wrote the book in 1486/7, a writer of pure and elegant classicising verse and a seller of indulgences (a revealing combination!). It includes a very long Genethliacon dedicated to the recently-named Arthur, later Prince of Wales ... in Phalaecian hendecasyllables. And I have spotted a quotation from Martial in something else Gigli wrote: which seems to me very probably to settle the question of where this fascinating generation of circa 1500 Humanists got that metre from.
Incidentally, Gigli's genethliacon begins with a recusatio explaining that disertiores will be able to do his high subject justice in heroic measures. As people scrambled for favour and jobs in the new Tudor court, it was clearly important for him to do a quick job. Indeed, many of us, I suspect, found when we were schoolboys that hendecasyllables are just about the easiest metre in which to write fast. I wonder if that is why Erasmus produced Phalaecians to be hung up where Colet's schoolboys would see them, so that the little chaps might be tempted to have a go at doing it themselves.