The Codex Vaticanus is one of the oldest and most respected extant manuscripts of the Greek Bible (Old and New Testament), with three lacunae. The codex is named for its residence in the Vatican Library, where it has been held since the 15th century. It is written in Greek, on 759 vellum leaves, with uncial letters, and has been dated palaeographically to the 4th century. The manuscript became known to Western scholars as a result of the correspondence between Erasmus and the prefects of the Vatican Library. Portions of the codex were collated by several scholars, but numerous errors were made in the process. The codex's relationship with the Latin Vulgate was also poorly understood. As a result scholars were not initially aware of the codex's value. This changed in the 19th century, when transcriptions of the full codex became available. Scholars realised that its text differed from both the Vulgate and the Textus Receptus. Scholars now agree that the Codex Vaticanus contains one of the best texts of the New Testament in Greek, with that of the Codex Sinaiticus as its only competitor. Until the discovery by Tischendorf of the Sinaiticus text, it was without a rival in the world.