When were macrons first used to mark Latin text?

Question

A macron is a diacritical mark, which, in modern Latin texts, is sometimes used to mark a long vowel: ā, ē, ī, ō, ū, ȳ. From Roman uses of diacritical marks, I understand that the ancient Romans did not use macrons (they occasionally used an apex instead).

So my question is: when were macrons first used to mark Latin text? I'll keep it general, and not limit it to the way macrons are used today, in case they were originally used for some other purpose besides marking vowel length.

Answer 1

This is what I’ve been able to find – thanks to Oliver 1966.

Oliver 1966 (in footnote 42) mentions two documents important to us, both of them most likely were schoolbook texts:

• A fifth-century fragment from Virgil (text number 11 in Cavenaile Corpus papyrorum Latinarum);

• a leaf from a parchment codex of Juvenal (sixth century AD) – it is text number 37 in Cavenaile Corpus papyrorum Latinarum; also known as the Antinoë fragment of Juvenal.

As you can see from the screenshots above,

both macra and breves are used for vowel length (long and short vowels respectively).

Roberts 1935 writes that “marks of quantity are used haphazardly and by no means correctly throughout the text” (pp. 201-202). He also argues that such accentuation symbols were “not unknown” but “by no means uncommon” in Latin manuscripts from Egypt.