The Three Cantos published in the Chicago magazine Poetry in June-July-August 1917 are Pound's first attempt at beginning the long poem he had been thinking about since 1904-1905. He was not happy with them and started changing them even before they were published. He discarded them altogether when he published A Draft of XVI Cantos in 1925. But the Three Cantos stayed in print and rather than a false start, they should rather be regarded as the laboratory of the cantos to come. Topics, themes, images presented here were taken up again in the poem. And the last part of Three Cantos III was reworked to become Canto I. If Pound had been looking for a way to begin, the writing of these "discarded" cantos was his way of experimenting with available possibilities.
"Pound's recent unfinished epic, three cantos of which appear in the American edition of Lustra, proceeds by a very different method than that of Joyce in Ulysses. In appearance, it is a rag-bag of Mr. Pound's reading in various languages, from which one fragment after another is dragged to light, and illuminated by the beauty of his phrase. [...] And yet the thing has, after one has read it once or twice, a positive coherence; it is an objective and reticent autobiography."
T. S. Eliot. "A Note on Ezra Pound." (To-Day, 4 Sept 1918).