This passage was written by Thomas Hoccleve (1367?-1426), a rough contemporary of Chaucer.  Hoccleve worked at the Privy Seal office as a kind of civil servant preparing and copying government business--a human Xerox machine, in other words.  Hoccleve was also a poet of some note, and in the passage below from his Regiment of Princes, Hoccleve comments on the physical pain endured by the medieval scribe.  The excerpt below  comes from the electronic edition of Thomas Hoccleve: The Regiment of Princes, edited by Charles R. Blyth, originally published in Thomas Hoccleve: The Regiment of Princes, Kalamazoo, Michigan: Medieval Institute Publications, 1999.  See http://www.lib.rochester.edu/camelot/teams/hoccfrm.htm

...
"Many men, fadir, weenen that wrytynge
No travaille is; they holde it but a game;
Aart hath no fo but swich folk unkonnynge.
But whoso list desporte him in that same,
Let him continue and he shal fynde it grame;
It is wel gretter labour than it seemeth;
The blynde man of colours al wrong deemeth.

"A wryter moot thre thynges to him knytte,
And in tho may be no disseverance:
Mynde, ye, and hand - noon may from othir flitte,
But in hem moot be joynt continuance;
The mynde al hool, withouten variance,
On ye and hand awayte moot alway,
And they two eek on him, it is no nay.

"Whoso shal wryte, may nat holde a tale
With him and him, ne synge this ne that;
But al his wittes hoole, grete and smale,
Ther muste appeere and holden hem therat;
And syn he speke may ne synge nat,
But bothe two he needes moot forbere,
His labour to him is the elengere.

"Thise artificers see I day by day,
In the hootteste of al hir bysynesse,
Talken and synge and make game and play,
And foorth hir labour passith with gladnesse;
But we laboure in travaillous stilnesse;
We stowpe and stare upon the sheepes skyn,
And keepe moot our song and wordes yn.

"Wrytyng also dooth grete annoyes thre,
Of which ful fewe folkes taken heede
Sauf we ourself, and thise, lo, they be:
Stommak is oon, whom stowpynge out of dreede
Annoyeth sore; and to our bakkes neede
Moot it be grevous; and the thridde oure yen
Upon the whyte mochil sorwe dryen.
"What man that three and twenti yeer and more
In wrytynge hath continued, as have I,
I dar wel seyn, it smertith him ful sore
In every veyne and place of his body;
And yen moost it greeveth, treewely,
Of any craft that man can ymagyne.
Fadir, in feith, it spilt hath wel ny myne. (ll. 988-1029)