In 1568 the Flemish geographer Gerhard Kremer (better known by the Latinized version of his last name, Mercator) put out a map of the world plotted in such a way that the rhumb lines were straight. Maps for navigation based on Mercator's scheme could be easily marked with rhumb lines, and many of them were therefore put in, crossing and crisscrossing.

What's more, the sixteenth-century explorations had led to an increasingly detailed knowledge of the Americas ("The Indies"), and about the time that Twelfth Night was being written, a new map, with numerous rhumb lines, was published, showing the New World in far greater and more accurate detail than had ever been shown before. This added detail was the "augmentation of the Indies."

Maria tells Olivia that Malvolio seems to be raving, and when he appears on the scene, grotesquely clothed and quoting meaningfully from the letter, Olivia, flabbergasted, can only think he really is mad.

Malvolio is so far gone in self-delusion, however, that he interprets everything in the light of Olivia's supposed love for him, and in the midst of his triumphing, he remembers to be pious, saying:

—Act III, scene iv, lines 87-88

This is undoubtedly intended to mock Puritan sanctimoniousness, and, just as undoubtedly, the real Malvolio would have said "God" or "the Lord" or "the Almighty." Growing Puritan strength, however, in later years clamped down on references to God on the stage, and this form of ridiculous censorship led to the foolish substitution of "Jove."

Sir Toby conies fussing in, full of mock concern over Malvolio's madness, and saying:

—Act III, scene iv, lines 89-92

This is a reference to one of the examples of demonic possession in the New Testament. When Jesus asks the name of the "unclean spirit" possessing a man, that spirit answers "My name is Legion: for we are many" (Mark 5:9).

Toby baits Malvolio with his supposed madness and when the latter rushes off in a fury, Toby arranges to have him placed in a dark room because of his supposed madness, so that the practical joke may continue.

Meanwhile the affair of Sir Andrew and Viola/Cesario is developing further. Sir Andrew has written a cautiously phrased and clearly cowardly letter. Sir Toby accepts it gravely, but does not deliver it. He intends to deliver a challenge verbally, enormously exaggerating Sir Andrew's fire-eating propensities. He will then report with equal exaggeration to Sir Andrew, concerning what a raging fury Viola/Cesario is in. He says:

—Act III, scene iv, lines 203-4

The cockatrice is the fabulous serpent which can kill by his mere glance (see page I-150).

There now begins a series of mistakings very like those in The Comedy of Errors, complicated by difference in sex.

Antonio, the captain who has befriended Sebastian, has given him a purse of money to use, then follows him to keep an eye on him and guard him…

Meanwhile, Viola/Cesario, coming for another interview with Olivia, is waylaid by Sir Toby, who delivers Sir Andrew's challenge. The frightened Viola/Cesario finds he must fight the frightened Sir Andrew, but before anything can happen, Antonio comes charging in.

Assuming that Viola/Cesario is Sebastian, he is about to begin a fight in good earnest, when the Duke's officers come in to arrest him on the old charge of piracy. Antonio must ask Viola/Cesario to return his bag of money, for a fine may save his life. Naturally, Viola/Cesario knows nothing about the money, and Antonio is greatly upset over this seeming perfidy as he is dragged away.

And Sebastian too has his share of the confusion. Olivia encounters him, thinks he is Viola/Cesario, and begins to speak of love. Sebastian finds this entirely to his liking and says:

—Act IV, scene i, lines 61-63

Lethe was the name of one of the rivers of Hades, according to Greek mythology. All spirits were forced to drink of it, for it had the property of inducing forgetfulness so that past life on earth vanished from memory and only the spirit world remained. Sebastian is wishing, then, to forget his past existence and to live only in the present one, in which beautiful loving women appear from nowhere.

But the Malvolio affair is not yet done. Malvolio is now locked in a dark room and Sir Toby plans a further torment. He will have the Clown personify a curate, "Sir Topas," who will pretend to examine Malvolio.

The Clown demonstrates his skill at the part by talking a little learned-sounding gibberish. He says:

—Act IV, scene ii, lines 13-16

Gorboduc was a legendary king of early Britain, and in 1562 he was the subject of a play written by Thomas Norton and Thomas Sackville. In this play, Gorboduc divided his kingdom between two sons, Ferrex and Por-rex, and civil war followed. It was the first blank-verse tragedy published in England and began the cycle of drama that culminated so rapidly in the Shakespearean climax.

The Clown now begins the discussion with Malvolio through the closed door and is merciless. He insists the room in which Malvolio has been locked is not dark and that it is only the latter's mad imagination that makes it seem dark. The Clown says:

—Act IV, scene ii, lines 43-45

The "fog" spoken of here is the ninth plague brought down on Egypt by Moses prior to the Exodus. It is mentioned in Exodus 1:22-23: "And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days: They saw not one another, neither rose any from his place for three days."