From The Modern Word (an excellent website for postmodern literature):
Lesbare und lesenswerthe Bemerkungen über das Land Ukkbar in Klein-Asien
Johann Valentin Andreä Strassburg, Lazarus Zetzner, 1641.
- A very rare work of which only seven original copies survive, this fictional travelogue was written by J. V. Andreä, the purported author of Chymische Hochzeit Christiani Rosencreuz and "accidental" founder of the Rosicrucian movement. Author of several works involving imaginary communities and mystico-Christian utopias, including the Reipublicae Christianopolitanae Descriptio, Bemerkungen was an expansion of ideas first expressed in the Christianopolis, now projected onto an abstract philosophical country situated within the borders of present-day Iraq. While certainly of interest to Borges scholars and modern Rosicrucians, Bemerkungen is most notorious for its chapter on the ideal community of Vheissu, the major inspiration behind the infamous Zweite Fruchtbringende Gesellschaft. Better known to history as the Commune of Prague, the ZFG was an isolated group of philosophers, Rosicrucians, and Lutheran radicals who attempted to recreate the ideals of Vheissu by establishing a closed community outside Prague in 1773. Their experiment was a disaster, ending two years later in a spiral of cannibalism, violent orgies, and mass suicide. (For further details, see "Rosiges Glühen, Blutiges Kreuz," by Kristoph Gross, Der Annalen Metakarus, 1934, pp. 345-78; or "The Prague Commune and its Influence on DeSade's The 120 Days of Sodom," by Josephine Pinto, Lingua Franca, Vol 10/No. 3, April 2000, pp. 22-25.)
Read more at The Modern Word...
From Molly Hite's Ideas of Order in the Novels of Thomas Pynchon:
- "If "Vheissu" encodes anything, it is a pun "Wie heisst du?," "What is your name?" that parodies Stencil's preoccupation with sub rosa identities." 
- "George Levine cites in addition vécu, "Sartre's term for 'lived experience,'" and Richard Leverenz's "V. is you," reinforcing the suggestion that Vheissu is as overdetermined as V." 
Vheissu could also be constructed by dropping a few letters from the German word "Verheißung," promise or prophecy (ß is another character for ss).