[1356] Whoever fully understood the eye faculty (cakkhundriya), did he develop the 'I shall come to know the unknown' faculty (anaññātaññassāmītindriya)?
Yes.
Or rather, whoever developed the 'I shall come to know the unknown' faculty, did he fully understand the eye faculty?
Six persons developed the 'I shall come to know the unknown' faculty, but they did not fully understand the eye faculty; the Arahant both developed the 'I shall come to know the unknown' faculty and fully understood the eye faculty.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.