Frank, Yes I had read somewhere that he habitually carried it rolled in a small ball, being a blueish paste, in a white paper envelope in his vest pocket, and took it as he thought he needed to.

As for the doctor in the Whitehouse conviencing him not to take it, I don't think that is true. First, of all Blue Mass was too commonly prescribed by the doctors of the day to the soldiers in the hospitals. Lincoln's doctor telling him not to take it would have been against the normal practise.

Second, there is a picture of Lincoln either in 1864 or '65 maybe the last picture taken of Lincoln before he meets John Wilkes Booth. As Grandma would say Lincoln in that picture "looked like death warmed over".

Most attribute this look to the stresses of the office on Lincoln during the War. And I will agree that those were probably very great. But If you look closely at the eyes and cheeks It almost looks like the photograph of the Ukrainian President who was poisoned by radioactive material in his soup.

Could that photograph of Lincoln be showing the effects of Mercury poisoning?