Giacomo Casanova describes in his memoirs several meetings with the "celebrated and learned impostor". Of his first meeting, in Paris in 1757, he writes:
The most enjoyable dinner I had was with Madame de Robert Gergi, who came with the famous adventurer, known by the name of the Count de St. Germain. This individual, instead of eating, talked from the beginning of the meal to the end, and I followed his example in one respect as I did not eat, but listened to him with the greatest attention. It may safely be said that as a conversationalist he was unequalled.
St. Germain gave himself out for a marvel and always aimed at exciting amazement, which he often succeeded in doing. He was scholar, linguist, musician, and chemist, good-looking, and a perfect ladies' man. For awhile he gave them paints and cosmetics; he flattered them, not that he would make them young again (which he modestly confessed was beyond him) but that their beauty would be preserved by means of a wash which, he said, cost him a lot of money, but which he gave away freely.
He had contrived to gain the favour of Madame de Pompadour, who had spoken about him to the king, for whom he had made a laboratory, in which the monarch — a martyr to boredom — tried to find a little pleasure or distraction, at all events, by making dyes. The king had given him a suite of rooms at Chambord, and a hundred thousand francs for the construction of a laboratory, and according to St. Germain the dyes discovered by the king would have a materially beneficial influence on the quality of French fabrics.
This extraordinary man, intended by nature to be the king of impostors and quacks, would say in an easy, assured manner that he was three hundred years old, that he knew the secret of the Universal Medicine, that he possessed a mastery over nature, that he could melt diamonds, professing himself capable of forming, out of ten or twelve small diamonds, one large one of the finest water without any loss of weight. All this, he said, was a mere trifle to him. Notwithstanding his boastings, his bare-faced lies, and his manifold eccentricities, I cannot say I thought him offensive. In spite of my knowledge of what he was and in spite of my own feelings, I thought him an astonishing man as he was always astonishing me.Myths, legends and speculations about St. Germain began to be widespread in the late 19th and early 20th centuries, and continue today. They include beliefs that he is immortal, the Wandering Jew, an alchemist with the "Elixir of Life", a Rosicrucian, and that he prophesied the French Revolution. He is said to have met the forger Giuseppe Balsamo (alias Cagliostro) in London and the composer Rameau in Venice. end quote from wikipedia
It is always interesting to hear accounts from famous people who actually knew the "Comte de Saint Germain like Casanova and Voltaire. For example, Voltaire in a letter to Peter the Great of Russia said of Saint Germain, "He is a man who knows everything and who never dies." Voltaire lived until 1778 and Peter the Great lived until he was assassinated in 1762.
If you read accounts of the Comte de Saint Germain and you consider the possibility that he never died, one possible explanation was that he was a time traveler. In this way he could actually have known and done all the things he spoke about at that time to all these famous people.