Actually, it is in the power of Congress to coin money per the Constitution of the United States, Section 8 - Powers of Congress: To coin Money, regulate the Value thereof, and of foreign Coin, and fix the Standard of Weights and Measures; As for the nefarious 16th Amendment it was never ratified by a 3/4 quarter majority. From what I have read, only 2 states ever ratified it. As to what Lincoln was referring to was the issuing of interest free money.