The disclosure of future events is made through a dream, as was the experience for the prophet Daniel, which is recorded in the book with his name, or a vision as was recorded by John in the Book of Revelation.
Moreover, the manner of the revelation and the experience of the one who received it are generally prominent. The account is usually given in the first person. There is something portentous in the circumstances corresponding to the importance of the secrets about to be disclosed.
The element of the mysterious, often prominent in the vision itself, is foreshadowed in the preliminary events. Some of the persistent features of the apocalyptic tradition are connected with the circumstances of the vision and the personal experience of the seer.
The primary example of apocalyptic literature in the Hebrew Bible is the book of Daniel.
After a long period of fasting, Daniel is standing by a river when a heavenly being appears to him, and the revelation follows (Daniel 10:2ff). John, in the New Testament Revelation (1:9ff), has a like experience, told in very similar words.
Compare also the first chapter of the Greek Apocalypse of Baruch; and the Syriac Apocalypse of Baruch, vi.1ff, xiii.1ff, lv.1-3. Or, as the prophet lies upon his bed, distressed for the future of his people, he falls into a sort of trance, and in "the visions of his head" is shown the future.
This is the case in Daniel 7:1ff; 2 Esdras 3:1-3; and in the Book of Enoch, i.2 and following. As to the description of the effect of the vision upon the seer, see Daniel 8:27; Enoch, lx.3; 2 Esdras 5:14.