The oldest surviving printed Cornish is in a book by Andrew Borde, published in 1540. "In Cornwall is two speches: the one is naughty Englysshe and the other is Cornysshe speche. There be many men and women the whiche cannot speake one worde of Englysshe but all Cornysshe." 1/7 
Andrew Borde has 3 pages on the Cornish language in his 1540 "The Book of the Introduction of Knowledge", including all numbers up to 30, saying "no Cornyshe man dothe number above xxx, and this is named, Deec warnegons. And whan they have told thyrty, they do begyn agayn." 2/7
Here are the numbers from one to nine in Cornish from Andrew Borde's book. 3/7
... and here now are the numbers from 10 to 30. 4/7
Borde includes twenty-four sentences of use to travellers, which represent an imaginary conversation between a stranger and his hostess at an inn, and were obviously taken down by the author as he heard them. 5/7
Borde makes several disapproving references to Cornish food, and especially also to Cornish beer, of which he makes a native say:
It is thick and smoky and also it is thin,
It is like wash as pigs had wrestled therein.
6/7
It is thick and smoky and also it is thin,
It is like wash as pigs had wrestled therein.
6/7
The 1540 edition of "The Boke of the Introduction of Knowledge" is immensely rare - the @britishlibrary has a copy of course, but there is no example in private hands AFAIK. These scans come from a type facsimile, scarce in its own right, printed by William Upcott in 1814. 7/7
