Water, earth and air

[Jorge_Stolfi]

Nebuly lines as cosmic boundaries start to appear around 1300, and they are on full display in Christine de Pizan's Book of the Queen.  Nebuly lines occur in early heraldry, but they are uncommon. [...] German heraldry used the term 'gewolkt' from 'die Wolke' also meaning cloud. Form and definition were well established before the 15th c.

But we must distinguish the "nebuly line" of heraldry from the "wolkenband" of cosmic diagrams.  

The former is a simple wavy line with swollen fingers.  I understand that it is meant to be a highly stylized representation of clouds, but in the example you gave it only refers to the family's name, with no cosmic implications.

The "wolkenband", on the other hand, while it started as a depiction of a stream of cloud too, it soon evolved to a specific graphical convention: scalloped band that looks like a pleated ribbon with frilled edge, with details that suggest a third dimension.   For all I have seen, it was specifically used to indicate the division of a figure into "Earthly" and "Heavenly" domains, the latter assumed to be beyond the vault of the sky.  Without that band, the image could be misread as if Jesus and other divine entities were present in person at a coronation, baptism, etc.  This "wolkenband" had no connection to heraldry, and I wonder if it was ever used in a blason.

Even ignoring its probable sourcing from the Oresme diagram, the figure of f69v3 almost certainly depicts the same concept of the cosmos: with "land" and the "waters below" (seas) at the center, surrounded by the stars, separated from the "waters above" by the vault of the "sky".  The wavy line of f68v3 should have been the latter, and therefore should have been a "wolkenband" as in the Oresme diagram -- not a nebuly line.  

But actually it is neither: it has a 3D effect (unlike the "nebuly line" of heraldry) but not the fine frills along the edge (unlike the standard "wolkenband").

Again, by the time the scribe got to draw the big fold-out f85v2, he apparently had learned how a wolkenband should be drawn, and put two passable ones around the Central and East rosettes.  (If he and/or the Author understood the meaning of that graphical device, that would imply that those rosettes are not supposed to be on Earth but in the Heavens.) 

All the best, --stolfi