I found this in a couple of AAO appeals for EB1OR (they use pretty much the same wording in all of them)
The submitted materials about Sigma Xi reveal that Sigma Xi invites to full membership "those who
have demonstrated noteworthy achievements in research." These achievements must be evidenced by
"publications, patents, written reports or a thesis or dissertation, which must be available to the
Committee on Admission if requested." A noteworthy achievement is not necessarily an outstanding
achievement. In fact, the record reveals that the society does not take a particularly strict view of
noteworthy achievements. Specifically, Philip Carter, the Executive Director of the association,
indicates that the "Committee on Qualifications and Membership interpreted this qualification to
include primary authorship of two papers." In addition, an earned doctoral degree may be substituted
for one paper. We cannot conclude that primary authorship of one or two papers is an outstanding
achievement in the beneficiary's field