Ghost-lore relevant to Hamlet

Other bits of popular ghost-lore find themselves incorporated in Hamlet. Here are a few examples.

1.) Ghosts will not speak until addressed by some mortal. (Wilson, p. 75)

BARNARDO. It would be spoke to.
MARCELLUS. Question it, Horatio. (I.i.45)

2.) Scholars come armed with the necessary formulae (presumedly in Latin) for exorcism if the spirit should prove to be an evil one. (Wilson, p. 76)

 Thou art a scholar. Speak to it, Horatio. (I.i.42)

Let's call the butler up, for he speaks Latine,
And that will daunt the devil.  --John Fletcher, The Night-Walker, c.1611, II,i.

3.) Spectres are likely to lead a person to a high spot and there drive him or her mad. (James I. p.63)

HAMLET.It waves me forth again. I'll follow it.
HORATIO. What if it tempt you toward the flood, my lord,
   Or to the dreadful summit of the cliff
   That beetles o'er his base into the sea,
   And there assume some other horrible form
   Which might deprive your sovereignty of reason
   And draw you into madness? (I.iv.69-74)

4.) Persons affected by mania or melancholy are most commonly subject to receive false imaginations and phantasms. (le Loyer, p.104)
      
Father Noel Taillepied presents further information on this theory. Certainly it is relevant to Hamlet's own madness.

This evil Spirit goeth about seeking whom he may devour, and should he chance to find a man, already of a melancholic and Saturnian humour, who on account of some great losses, or haply because he deems his honour tarnished, the demon here has a fine field to his hand, and he will tempt the poor wretch to depths of misery and depression.  --Father Noel Taillepied, A Treatise of Ghosts (1588), trans. Montague Summers, London, Fortune Press [1933], p.95.

Hamlet, himself, expresses concern that his "melancholy" may make him further susceptible to demonic visitations.

          The spirit that I have seen
May be the devil, and the devil hath power
T' assume a pleasing shape; yea, and perhaps,
Out of my weakness and my melancholy,
As he is very potent with such spirits,
Abuses me to damn me. (II.ii.610-615)