Merrill's work sheets reveal his ingenuity with the sonnet form. Manuscript 3, 6, and 7 give us a date, "6 Sept 62." Manuscript 9 shows that Merrill crossed out an earlier title, "TRAVEL," and replaced it with "The 1002nd Night." Manuscript 10 suggests other possible titles, such as "FROM A TRAVELLER'S DIARY."
Stephen Yenser comments on the sonnet form in The Consuming Myth: "'Rigor Vitae' begins with a series of quatrains that is broken off, as David Lehman has noticed, just in time to turn the passage into a sonnet. Merrill breaks into the fourth quatrain after one and a half lines, rhymes the last words in these lines with end words in the third quatrain, and thereby laces the last lines up into a sestet (abbaba)--though the sestet is hard to pick out as such. The interuption is abrupt, the sonnet's last line is really more a hemistich, and it is in German to boot ('Dahin! Dahin!), so the rhyme is diguised" (124-25).