A perfect input device will have no impendance, and a perfect output device will have infinite impendance. In real terms, usually the impedances of outputs are 5 to 10 times that of standard inputs for acceptable performance. Anything less could result in distortion of sound. In effect, the output would not be capable of putting out enough clear signal for the input to pick up properly. As an example, dynamic microphones typically have impedances of 300ohms to 600ohms.
Condenser microphones have impedances in the thousands.
Line outputs approach 10kohms. Mixer inputs try to have impendances as low as possible to minimize distortion of the sound. Some mixers tout 'Very Low Impedance' or 'VLZ' as a feature of their mixers, which affects microphone inputs more audibly than line inputs. The fact that output impedance is always much greater than input impedance also means that most high-impedance outputs can power multiple inputs at one time. A simple splitter cable would be able to allow two inputs to receive a clear signal from one output, or possibly even more.