What was the archaic source of "All Turns To Yesterday"?

Question

I was recently reminded of Mediæval Bæbes' performance of "All Turns To Yesterday" (perhaps best known from its adaptation into Delerium's Aria).

I've read that it's a rendition of a traditional Middle English poem (lyrics quoted below), but I can't find any information about what the source of this poem or its provenance might be.

The grammar and lexicon sounds to me like it's been somewhat modernized, which may be why I can't find anything when I search on the lyrics, or maybe it's just because Google is overwhelmed with references to the Delerium song.

Is this poem attributed in any historical source? Do we know who wrote it and when?

I have wist, sin i couthe meen,
That children hath by candle light
Her shadewe on the wal iseen,
And ronne therafter all the night.

Bisy aboute they han they han ben
And whom they catchen it best wolde wene

I have wist, sin i couthe meen,
That children hath by candle light
The shadewe catchen they ne might,
For no lines that they couthe lay.
This shadewe i may likne aright
To this world and yesterday.

Answer 1

It turns out this poem is from the Vernon manuscript in the Bodleian Library, written in the late 14th century.

After a lot of searching on specific substrings I found that the lyrics sung by the Mediæval Bæbes seem to have been taken from Reginald Thorne Davies' Medieval English Lyrics: A Critical Anthology (1964). These particular verses are on page 118 of that book, but they're a fragment of a much larger poem.

The notes at the back of that book in turn somewhat cryptically cite it as:

Index 3996. Bodl. MS. (Vernon) Eng. poet 2.I (3938), f.408a. C.B. 14c., p. 143, no.101

which, so far as I can tell, means that it's #3996 in Brown and Robbins' Index of Middle English Verse and on folio 408.a of the Vernon manuscript.