Edgar comes on stage in some fashion that prevents him seeing Kent asleep in the stocks. In a monologue he discloses his intentions to adopt the look, dirtiness, and manner of a guest at Bedlam, the Bethlehem hospital for the insane. He is so good at this that he will not be recognized even by his own father in Acts III and IV.
ACT II. SCENE II. SEGMENT B. A wood nearby.
I heard myself proclaimed, 
And by the happy hollow of a tree
Escaped the hunt. No port is free, no place
That guard and most unusual vigilance
Does not attend my taking. While I may scape,
I will preserve myself, and am bethought 
To take the basest and most poorest shape
That ever penury in contempt of man
Brought near to beast. My face I’ll grime with filth,
Blanket my loins, elf all my hair in knots,
And with presented nakedness outface 
The winds and persecutions of the sky.
The country gives me proof and precedent
Of Bedlam beggars who with roaring voices
Strike in their numbed and mortified bare arms
Pins, wooden pricks, nails, sprigs of rosemary. 
And with this horrible object, from low farms,
Poor pelting villages, sheep-cotes, and mills,
Sometime with lunatic bans, sometime with prayers,
Enforce their charity. “Poor Turlygod! poor Tom.”
That’s something yet. Edgar I nothing am.