"Sanmai Hottokuki" is a legendary diary which is said to be written by our Master Honen, starting from January 1st, 1198 (when he was 66 years old) to January 4th, 1206 (when he was 74yrs old).
The word, Sanmai Hottokuki can be divided into three parts; Sanmai, Hottoku and ki.
The first word, Sanmai (三昧) is a translation of "Samadhi" in Sanskrit which usually means higher level of concentrated meditation (*Wikipedia). According to the Japanese-English Buddhist dictionary, Sanmai means " Concentration of the mind on a single object" or simply "meditation".
Next, Hottoku (発) can be also divided into two words; Ho(Hotsu)発 and Toku得. " Ho(Hotsu )"or "Hatsu"発means "to appear and birth" and "toku(得)" means "to gain or to attain."
So" Sanmai Hottoku (三昧発得）" usually means " to attain higher level of meditation. " However in Jodo tradition, "Sanmai Hottoku" specifically means "to attain visualization of Amida Buddha and his pure land."
The last word, "Ki (記)" means a record or diary but this Sanmai Hottokuki-diary was neither written every day nor written in detail. It was more like memo. The reason why I used the word "legendary" was because the existence of "Sanmai Hottokuki" was just mentioned in old documents. Till today, there is no original document of "Sanmai Hottokuki" found.
One of the documents which referred the existence of Master Honen's "Sanmai Hottokuki" are
1 . Honen Shonin Denki, so-called "Daigobon" (醍醐本『法然上人伝記』) which was said to be one of the oldest biographies of Honen Shonin, written by Seikanbo Genchi (1183-1238) or his disciples. For a long time this biography was lost but discovered in 1917. Now it is well-known as "Daigobon edition" named after the Daigoji Sanboin Temple where they discovered this book.
2. Saihoshinan-sho (西方指南抄、中本）written by Shinran Shonin around 1256-1257 (when Shinran Shonin was 84 to 85 years old, he transcribed Master's words from the collections of Genchi.
3. Shui Kurodani Shonin Gotouroku (拾遺黒谷上人語燈、巻上)by Doko Ryoe around 1274.
Kurodani Shonin Gotoroku is a collection of words, letters, and sermons of the Master Honen, edited by his disciple's disciple, Ryoe Doko Shonin from November 1274 to January 1275. Kurodani Shonin is another name (nickname) of Master Honen. Total of the Volumes of the collection is 18 Volumes. They can be divided into 3 categories and called as follows;
I. 1st to 10th Volume: Kurodani Shonin Kango Touroku or "Kango Touroku", written in Chinese characters.
II. 11th to 15th Volume: Kurodani Shonin Wago Touroku or " Wago Touroku", written in Japanese. This was translated in English (Promise of Amida Buddha.)
III. 16th to 18th Volume: Shui Kurodani Shonin Gotouroku or "Shui Touroku", written in both Chinese and Japanese. "Shui" means " to pick up later the important words (that they missed)."
*Sanmai Hottokuki is written in Chinese in the volume 16th.
All sources are available at Jodoshu Zensho.
4. The forty eight biographical picture scrolls of Honen Shonin （四十八巻伝）(around 1307).
This is a national treasure of Japan and this book of biographical scrolls, has lots of ”another (nick)name" such as"Honen Shonin Shiju hachi (48) kan den" , "Honen Shonin Gyojoezu" or "Chokushu Goden" or its abbreviation, "Chokuden." This was translated in modern Japanese by Jodo Shu Reserach Institute and available to buy online. http://press.jodo.or.jp/products/detail.php?product_id=249
Actually there are more biographies of Honen Shonin and Jodo Shu Research Institute listed 6 major biographies here.
I also searched "Sanmai Hottokuki" at the Jodoshu Zensho and nine titles of the book or paper hit . But of course, no Enlgish translations. So I'd like to select to explain the four documents above which contains Master Honen's diary so called "Sanmai Hottokuki."