I have previously posted on the fragments of Melito De anima et corpore.
Although I do not have full access to the witnesses, I have the Syriac under the name of Alexander of Alexandria and the Coptic under the name of Athanasius through E.A. Wallis Budge, Coptic homilies in the dialect of Upper Egypt (London: British Museum, 1910).
My reading today was undertaken as a spiritual exercise at a time when normally I would be saying mass (but was prevented from doing so by government regulation), but inevitably did not stay so. I observed that whereas the Coptic states that Christ rose from the dead “in the third (hour) of the day” (ϩⲙ̄ⲡⲙⲉϩϣⲟⲙⲛⲧ ⲛ̄ϩⲟⲟⲩ) the Syriac reads “on the third day” (ܠܬܠܬܐ ܝܘܡܝܢ).
Whereas it might be obvious that the Syriac has rendered τῃ τρίτῃ τῆς ἡμέρας as though it were τῃ τρίτῃ ἡμέρᾳ (a simple enough mistake, given that this is a familiar phrase) there is more. Epistula apostolorum 15 implies that the paschal vigil is to conclude at 3am, a direction made explicit in Didascalia apostolorum 5.19.6 (part of chapter 21 in the Syriac.)
On the assumption that the reading of the Coptic is correct this all implies that there was an established pattern of maintaining the vigil until 3am in Quartodeciman communities, a suspicion now confirmed by Melito. All I need to do now is persuade my parish that this is the best time for the Easter vigil!