Shortest XQuery quine

[David Sewell]

XQuery is one of those languages in which it's possible to write a
one-character quine (assuming you set the serialization options as
needed).

For example, using Saxon in a Unix-ish environment:

  echo 1 > quine.xqy
  java net.sf.saxon.Query quine.xqy \!method=text

produces the output "1".

(What other common languages similarly accept as input a single literal
value that is returned in output?)