According to Douce's MS. Notes, on St. Martin's night boys expose vessels of water, which they suppose will be converted into wine.  The parents deceive them by substituting wine.  In the Popish Kingdome we read—

To belly cheare yet once againe doth Martin more encline,
Whom all the people worshippeth with rosted geese and wine;
Both all the day long and the night now ech man open makes
His vessels all, and of the must oft times the last he takes,
Which holy Martyn afterwarde alloweth to be wine;
Therefore they him unto the skies extoll with prayse devine,
And drinking deepe in tankardes large, and bowles of compasse wide;
Yea, by these fees the schoolemaisters have profite great beside:
For with his scholars every one about do singing go,
Not praysing Martyn much, but at the Goose rejoyceing tho',
Whereof they oftentimes have part, and money there withall;
For which they celebrate this Feast, with song and musicke all. (Stanford)

(Observations on Popular Antiquities, Brand, 1877).