Lengthy letter (2 pages) handwritten and signed by R. Menachem Mann son of R. Baruch of Minsk, a Lithuanian spiritual giant. Neshviz (Nyasvizh, Belarus), Elul [1818].
The letter, which is addressed to his brother R. Baruch Shimon of Shklow, first deals with familial matters. R. Menachem Mann of Minsk, who was in Neshviz at the time, asks his brother to send a package to his wife who had remained in Minsk. He also writes about a trip to Eretz Israel. Further in the letter, he guides his brother in the approach to faith and trust in G-d, and gives him interesting advice regarding the ways of teaching Torah to students.
Most of the letter (over a page) contains guidance regarding giving lectures. R. Menachem Mann, who was one of the greatest Torah disseminators in his times, advises his brother to accustom himself to studying and teaching with quick grasp and deep understanding. He describes the study program he scheduled for his students, which included both lectures and review. It appears from the letter that R. Menachem Mann would study four folios of Talmud in depth with his disciples, including Rashi and Tosafot (two folios of Tractate Bava Metzia and two folios of Tractate Chullin, with in-depth study of the topic and the relevant works of the Rishonim and poskim).
R. Menachem Mann concludes the letter with his signature, "Menachem Mann son of R. Baruch", followed by an additional short letter of several lines to his relatives and acquaintances, signed a second time.
This letter is not known from any other source, and was presumably never published. There is one other letter by R. Menachem Mann, regarding faith, trust in G-d, and being satisfied with little, "Igeret R. M. MiMinsk", published by R. Shmuel Moltzan at the beginning of the book Emunah VeHashgachah – teachings of the Gaon of Vilna (Königsberg, 1864). This letter was later published in various editions of Igeret HaGra and Igeret HaRamban.
R. Menachem Mann of Minsk (d. 1834), prominent Lithuanian Torah scholar in the times of R. Chaim of Volozhin. In his generation he was known as "HaGaon HaChassid" for his exceptional brilliance in revealed and kabbalistic realms of the Torah, and for his wondrous, holy conduct (this title was also given to the Gaon of Vilna). A leading Torah disseminator in his times, yeshiva dean and maggid in Minsk. Many rabbis in Lithuania and Minsk were his close disciples.
He was born in Polotsk to R. Baruch Stolper. Orphaned at a young age, he was raised amongst the Torah scholars of Shklow. At the age of eight (!), he was renowned as a genius well versed in the entire Talmud. From a young age, he would study eighty folios of Talmud a day with Tosafot. When not yet twelve years old, he began studying kabbalah from R. Baruch, maggid in Shklow. He married the daughter of R. Avraham son of R. Asher Anshel, a rabbi of Minsk and author of Amud HaYemini (Minsk, 1811). He was referred to in Minsk as R. Mandel (in their approbations to his book Zichron Menachem, the rabbis of Minsk also refer to him as R. Mandel, describing him as an outstanding and pious Torah scholar).
He disseminated Torah in the Batei Midrash and yeshivot of Minsk, and many Lithuanian Torah scholars were his disciples (such as the Oneg Yom Tov and others). His absolute dedication to Torah study, which is evident in the present letter, is also mentioned in Eisenstadt's book Rabbanei Minsk VeChachameha (p. 27), where R. Mandel is described as one who never ceased teaching Torah to his disciples, attempting to instill in them positive character traits and encouraging them to refrain from indulgence. His epitaph contains exceptional praise of his Torah prominence and diligence (Rabbanei Minsk VeChachameha, pp. 41-42).
A small part of his teachings was printed in the book Zichron Menachem (Warsaw, 1874), published by his son R. Yisrael Chaim Klein, and in She'erit Binyamin (Jerusalem, 1863), published by his disciple R. Binyamin Rabbi of Stołpce (who immigrated to Jerusalem), who writes: "R. Menachem Mann… whose exceptional piety and asceticism were renowned… he devoted himself body and soul to disseminating Torah… producing prominent rabbis… he received several rabbinic appointments from large, famous town, yet he didn't wish to take on a rabbinic position, preferring to continue disseminating Torah and edifying disciples".
His brother, recipient of the letter, R. Baruch Shimon, later served as maggid in Shklow, and he is mentioned in the foreword to Zichron Menachem as the one who gave the writings for publication.

[1] leaf, written on both sides and signed twice. 21 cm. Thick blue paper. Fair condition. Stains. Tears and wear, worming and folding marks. Text faded and slightly damaged in several places.