In 1584 Dee and Kelley were asked to make a book of silvered leaves where the angels would miraculously write the Book of Loagaeth for Dee. This was to be prepared before August 1st 1584 and they were told by the angels to be in Prague by that time.
From Casaubon p. 217 Madimi isn't very happy about the fact that Dee failed to produce the book for them:
...For August past is the first day: And Mapsama wanteth, not by himself, but through your negligence: whose fingers wrought, and made en end of anothers work, which was tied to time.
Nalvage was beaten from you... ...with whom [Nalvage] you now have no power. For the receiver and giver for that time, were of time.
The way I interpret this is that there were some conditions in Prague on/before Aug 1st that were beneficial and unique (probably relating somehow to the planetary/zodiacal attributes of Nalvage and Mapsama) for the miracle to happen. It would be interesting to know what the sky looked like at that time in Prague, especially compared to Cracow from where they left.
Anyone have any ideas about how Nalvage and Mapsama tie into the enochian hierarchy? All that can be found in the MS is that they're both serving under Gabriel, and their names are "Earth Fleer" (= Nalvage) and "He That Speaks" (= Mapsama) in english. Nalvage is also said to be "a close kinsman" to Galvah (= I am the End), the mother of Madimi. This would tie him to the planetary hierarchy of the Sons and Daughters of Light.
Edit:
Here are the positions of the planets if someone can make more sense out of them:
http://www.astro.com/swisseph/ae/1500/ae_1584.pdf