Platinum was worked in South America long before Europeans could do anything with it. Objects combining platinum and gold, made by sintering rather than melting, come from the coast of what is now Ecuador and are associated with the La Tolita culture, from roughly the last centuries BCE into the early centuries CE. Melting was out of the question: platinum does not soften below about 1768 degrees C, far beyond any furnace of the period anywhere in the world.
Spanish colonists in the gold workings of the Choco region of Colombia encountered it as an unwanted heavy white grit that could not be separated from the gold and could not be melted out. They called it platina, a diminutive of plata, silver, meaning something like inferior little silver, and there are accounts of it being thrown back into the rivers.
Antonio de Ulloa, on the Spanish and French geodesic expedition to South America, described it in his published account of 1748, which introduced the metal to European science. Charles Wood had independently brought samples to England from Jamaica in 1741. Working it required new techniques, and it was not routinely melted until the oxy-hydrogen torch and related methods of the nineteenth century.
The point for a book of correspondences is a negative one, and it should be stated plainly. Platinum arrived in the European scientific world in the middle of the eighteenth century, more than two centuries after the seven-metal scheme had already been broken by antimony, bismuth and zinc, and at the moment when the number of known metals was about to multiply many times over. No alchemical tradition assigned it anything. Any planetary or esoteric attribution of platinum is a modern construction, and dating it honestly means dating it to the twentieth century or later.