Mutual coupling among oscillators of an ensemble has been proposed to explain the precision of some circadian rhythms. Reciprocal triggering is one of the most familiar forms of mutual coupling in nervous systems, but it can at best produce only modest improvement in temporal precision. Nevertheless, models with an elementary elaboration of such coupling show that circadian precision could be derived from oscillators that are intrinsically "sloppy"; sufficient conditions are that output of the individual components be summed and that mutual triggering be mediated by a nonlinear phenomenon, such as a threshold.