Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[291] Moreover, Moses was the inventor of the form of their trumpet, which was made of silver. Its description is this: - In length it was little less than a cubit. It was composed of a narrow tube, somewhat thicker than a flute, but with so much breadth as was sufficient for admission of the breath of a man's mouth: it ended in the form of a bell, like common trumpets. Its sound was called in the Hebrew tongue Asosra. Two of these being made, one of them was sounded when they required the multitude to come together to congregations. When the first of them gave a signal, the heads of the tribes were to assemble, and consult about the affairs to them properly belonging; but when they gave the signal by both of them, they called the multitude together. Whenever the tabernacle was removed, it was done in this solemn order: - At the first alarm of the trumpet, those whose tents were on the east quarter prepared to remove; when the second signal was given, those that were on the south quarter did the like; in the next place, the tabernacle was taken to pieces, and was carried in the midst of six tribes that went before, and of six that followed, all the Levites assisting about the tabernacle; when the third signal was given, that part which had their tents towards the west put themselves in motion; and at the fourth signal those on the north did so likewise. They also made use of these trumpets in their sacred ministrations, when they were bringing their sacrifices to the altar as well on the Sabbaths as on the rest of the [festival] days; and now it was that Moses offered that sacrifice which was called the Passover in the Wilderness, as the first he had offered after the departure out of Egypt.