Ways to determine polarity (dc) without a meter
1: You can pass current from your source through a wire and check the direction of the magnetic field with a compass.

But, then, a compass is a meter also.

2: Make a circuit by connecting in series a battery, your source and a resistor. The configuration that dissipates more heat on the resistor (use your finger as a heat probe) is when DC source and battery are placed with the same polarity ( +DC- +BATT- R ).