Timothy Bright: A Treatise of Melancholy

If Elizabethans thought Hamlet was not entirely sane, they might have
understood his affliction as melancholy. There are many parallels between
Hamlet and Bright's 1586 description of the melancholy man.

This is an extract from chapter 22 of his study.

How melancholy altereth those actions which rise out of the brain.Touching actions which rise from the brain, melancholy causeth dullness of conceit, both by reason the substance of the brain in such persons is more gross,and their spirit not so prompt and subtle as is requisite for ready understanding.  Again, almost all the senses standing in a kind of passive nature, a substance cold and dry & and by consequent hard & is not so meet thereto; which, as it serveth well to retain that which is once engraven, so like adamant it keepeth, in comparison of other tempers, that which once it hath received: whereby as they are unfit to commit readily to memory, so retain they that is committed in surer custody. Sometimes it falleth out that melancholy men are found very witty, and quickly discern, either because the humour of melancholy with some heat is so made subtle that, as from the driest wood riseth the clearest flame, and from the lees of wine is distilled a strong and burning aqua vitae, in like sort their spirits, both from the dryness of the matter, and straining of the gross substance from which they pass, receiving a pureness, are instruments of such sharpness, which is the dry light that Heraclitus approved. To this, other reasons may be added, as: exercise of their wits, wherein they be indefatigable, which maketh them seem to have that of a natural readiness which custom of exercise, and use hath found in them. Moreover, while their passions be not yet vehement, whereby they might be overcarried, melancholy breedeth a jealousy of doubt in that they take in deliberation, and causeth them to be the more exact and curious in pondering the very moments of things. To these reasons may be added the vehemancy of their affections once raised: which carrieth them, with all their faculties thereto belonging, into the depth of that they take pleasure to inter-meddle in. For though the melancholy man be not so easily affected with any other passion as with those of fear, sadness, and jealousy, yet being once thoroughly heat with a contrary passion, retaineth the fervency thereof far longer time than any other complexion, and more fervently boileth therewith, by reason his heart and spirit hath more solidity of substance to entertain deeply the passion, which in a more rare and thin sooner vanisheth away. Thus greediness of desire in those things which they affect maketh them diligent and painful, wary and circumspect, and so in actions of brain and sense not infererior to the best tempers; as also it maketh them stiff in opinion. Their resolution riseth of long deliberation, because of doubt and distrust which, as it is not easily bred, so it is also hard to remove. Such persons are doubtful, suspicious and thereby long in deliberation, because those domestical fears, or that internal obscurity, causeth an opinion of danger in outward affairs where there is no cause of doubt. Their dreams are fearful, partly by reason of their fancy, waking, is most occupied about fears and terrors, which retaineth the impression in sleep; and partly through black and dark fumes of melancholy rising up to the brain, whereof the fantasy forgeth objects, and disturbeth the sleep of melancholy persons.