  Using a prototype of the Tomo-e Gozen wide-field CMOS mosaic camera, we
acquire wide-field optical images at a cadence of 2 Hz and search them for
transient sources of duration 1.5 to 11.5 seconds. Over the course of eight
nights, our survey encompasses the equivalent of roughly two days on one square
degree, to a fluence equivalent to a limiting magnitude about $V = 15.6$ in a
1-second exposure. After examining by eye the candidates identified by a
software pipeline, we find no sources which meet all our criteria. We compute
upper limits to the rate of optical transients consistent with our survey, and
compare those to the rates expected and observed for representative sources of
ephemeral optical light.
