I’ll silence me even here.

[III, iv, 4]

In the Quarto of 1603, Corambis (Polonius) is more explicit.

Madame, I heare yong Hamlet comming,

I’le shrowde my selfe behinde the Arras.

exit Cor.

[Sig. G2r]

Earlier in the play, in preparation for a different observation, Polonius arranged with the King to observe Hamlet as

he walks four hours together

Here in the lobby....