Masters Of Theosophy
The Mahatmas were the direct, in-person, instructors of Madame Blavatsky. They "wrote" letters to A.P. Sinnett by "precipitating" those letters apparently out of the air and the letters are currently in the British Museum. They are a mine of useful inspiring material. At the same time they must be read with some caveats. We only hear one side of the conversation. They are sometimes tailored to the individual receiving them. They sometimes speak colloguially/familiarly of their agent, Madame Blavatsky.
The letters appear in several books and have been placed online by the Theosophical University Press at: Mahatma Letters to A.P. Sinnett
We have included some research material by Daniel Caldwell showing that the Mahatmas had anticipated and even encouraged the publication of their letters - and showing why some contrary opinion had develped on this point. Two good articles dealing with the issue of the Mahatmas is one by Williiam Q. Judge, "The Mahatmas as Ideals and Facts," and his artilce, "H.P.B. On Messages From Masters."
The Great Master's Letter - This letter was printed in the magazine Lucifer in 1896, after the deaths of HPB (in 1891) and WQJ (in 1896). The letter was sent to Mr. Sinnet during the early days of the Theosophical Society, in answer to objections regarding the conduct of the Society.