It is richt facil and eith gait, I the tell,
Forto discend and pas on down to hell:
The blak gettis of Pluto, and that dirk way,
Standis evir oppin and patent nycht and day;
Bot tharfra to return agane on hyght,
And heir abufe recovir this aris licht,
That is difficil wark, thar lawbour lyis.
Source, in full
It is right facile and eith [easy] gait, I thee tell, / For to descend and pass on down to hell: / The black yetts of Pluto and that dark way / Stand ever open and patent night and day; / But therefra to return again on height, / And here above recover this air's light, / That is difficile work—there labour lies.
Notes from Wikiquote
Bk. 6, line 265