Detail of the column of Trajanus, depicting his Dacian wars. Here we see soldiers in a Testudo formation (tortoise). The section below should be an account of the end of the third Macedonian war (ca 168 Bc).
"Heracleum was taken in a peculiar manner. The town had a low wall of no great extent on one side, and to attack this the Romans employed three picked maniples. The men of the first held their shields over their heads, and closed up, so that, owing to the density of the bucklers, it became like a tiled roof."
Polybius - Histories XXVIII.11
Translated by W. R. Paton