A beam-normal single-spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable related to the imaginary part of the two-photon exchange process. We report a 2% precision measurement of the beam-normal single-spin asymmetry in elastic electron-proton scattering with a mean scattering angle of theta(lab) = 7.9 degrees and a mean energy of 1.149 GeV. The asymmetry result is B-n = -5.194 +/- 0.067(stat) +/- 0.082 (syst) ppm. This is the most precise measurement of this quantity available to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (theta(lab) -> 0) where they should be most reliable.
