Titus Livius (Livy), The History of Rome, Book 44
Alfred C. Schlesinger, Ph.D., Ed.

33. ... to gather, and finally he ordered the water-carriers to follow him to the sea, which was less than three-tenths of a mile away, and to dig wells on the beach, some here, some there, at slight intervals. [2] The immense height of the mountains,¹ especially inasmuch as they produced no visible rivers, gave him the hope that underneath were hidden streams, the veins of which trickled through to the sea and mingled with the salt water. [3] Hardly had the uppermost sand been penetrated when jets of water spurted out, at first muddy and slight, but then proceeding to pour out, as if by a miracle, with clear and copious water. [4] This success too gave the commander no little glory and power of leadership with the soldiers. Then when the soldiers were ordered to put their weapons in condition, the consul with the tribunes and ranking centurions went forward to reconnoitre the crossings, in order to find out where [p. 199]the way down was easy for men under arms and where² on the farther bank there was the least unfavourable way up. [5] After gathering sufficient information on these points, he introduced other changes, too; in the first place, he saw to it that everything in the column should take place in good order and without confusion at the beck and call of the commander; [6] when orders were given to the whole army at once and not all were within hearing, he said, some, after receiving an unclear order, made additions of their own and did more than was bidden, while others did less; hence discordant outcries arose everywhere and the enemy found out what was afoot sooner than one's own men. [7] Therefore the consul decided that the tribune of the soldiers should first give an order privately to the chief centurion of the legion, and he and his subordinates in rank should then each tell to the next in rank³ what was to be done, whether the order was to be passed from the head of the column to the rear, or from the last to the first. [8] The consul also made the innovation of forbidding sentries to carry a shield⁴ on post; for he said that a sentry is not going into combat to use his weapons, but is to keep on guard so that when he perceives the approach of the enemy, he may retire and rouse the others to arms. [9] Men set the shield before them and stand there, helmet on head; then when they are tired, they lean on the spear, rest the head on the shield-rim, and stand there drowsing, so that with their shining armour they can be detected by the enemy from afar, while they themselves do not see ahead at all. The consul also changed the practice of the outposts. [10] All were used to spending the entire day under arms, cavalry with their horses bridled; when this took [p. 201]place on summer days under an unremitting -and⁵ burning sun, after so many hours of heat and weariness the tired men and horses were often attacked by fresh enemy troops and superior numbers thrown into confusion by even a few. [11] So he gave orders that men on duty in the morning should be relieved at noon by a different afternoon detail; in this way a fresh enemy could never attack tired men.