The phrase more than meets the eye (also more than meets the ear) means: more significance or complexity than is at first apparent.

This phrase occurs, for example, in Hey Hey, My My (Into the Black), from Rust Never Sleeps (1979), by the Canadian-U.S. singer-songwriter Neil Young (born 1945) and the U.S. rock band Crazy Horse:

Hey hey, my my
Rock and roll can never die
There’s more to the picture than meets the eye
Hey hey, my my

The phrase first occurred as more is meant then [i.e., than] meets the ear in Il Penseroso, published in Poems of Mr. John Milton, both English and Latin, compos’d at several times (London: Printed by Ruth Raworth for Humphrey Moseley, 1645), by the English poet John Milton (1608-1674):

And if ought els, great Bards beside,
In sage and solemn tunes have sung,
Of Turneys ¹ and of Trophies hung;
Of Forests, and inchantments drear,
Where more is meant then meets the ear.

¹ The noun tourney denotes a knightly tournament.

In early use, the phrase more than meets the ear occurred in reference to John Milton’s Il Penseroso.—Two examples:

1-: From The Dublin Weekly Journal (Dublin, County Dublin, Ireland) of Saturday 14^th May 1726:

OUR Journalists have lately thought fit to communicate to the Publick several Translations of Odes from Horace. He is one of the Authors of Antiquity that can never be too much admired, for the Beauty and Variety of his Compositions, the Delicacy and Justness of his Reflections, and the inimitable Art he has of always appearing New every time he is Read; being every where so rich in Sense, that we are perpetually making new Discoveries in him, and may constantly apply to him Milton’s Character of that Noble Species of Writing,
Where more is meant than meets the Ear.

2-: From the Preface, by the Scottish philosopher George Turnbull (1698-1748), to Three Dissertations; One on the Characters of Augustus, Horace and Agrippa, with a Comparison between his two Ministers Agrippa and Mæcenas, by the Abbe de Vertot. […] Another on the Gallery of Verres, by the Abbe Fraguier […]. A third on the Nature, Origin and Use of Masks, in theatrical Representations among the Ancients, by Mr. Boindin (London: Printed for R. Dodsley, 1740):

To what important and profound Reflections Homer, Virgil, Horace, and other ancient Authors, lead those who read them with Intelligence, and are capable of entering into their Spirit: For in them and all good Writers, to use a Phrase of ‖ one who well deserves to be placed among the Ancients, More is meant than meets the Ear.

The earliest occurrences of the phrase more than meets the eye that I have found are as follows, in chronological order:

1-: From the opening lines of Memoirs concerning the City of Dublin, in 1755 and 56 ([s.l.]: [s.n.], 1757):

WHOEVER shall look studiously into the History of the great Cities of this Earth, their Situations, Constitutions, and Connections, their Growth, Vigour and Decay, will find therein much Matter of real Advantage and more Beauty in the moral Course of Things, than meets the Eye of a careless Observer.

2-: From the Preface, by the English clergyman John Upton (1707-1760), to Spenser’s Faerie Queene. A new Edition with a Glossary, and Notes explanatory and critical by John Upton (London: Printed for J. and R. Tonson, 1758), by the English poet Edmund Spenser (c.1552-1599):

What should hinder the poet, but want of art, from so contriving his fable, that more might be meant, than meets the eye or ear? cannot he say one thing in proper numbers and harmony, and yet secretly intend something else, or (to use a Greek expression) cannot he make the fable allegorical?

3-: From the review of An Apology for the Clergy. In which the Reasoning and Utility of the Bishop of London’s late Charge, are impartially considered (London: Printed for H. Payne, 1759), by R. Johnson—review published in The Critical Review: Or, Annals of Literature (London, England) of January 1760:

Our author concludes with some arguments ad hominem, and explains the nature of his lordship’s conduct while a private clergyman, in a manner which he thinks contradictory to his present charge to the clergy. But whatever might be the conduct of Dr. Sherlock ², we are apt to believe, that more is meant in our author’s defence of his brethren, than meets the eye; and that, while he vindicates the practice of the clergy, he is really stickling for pluralities.—A subject of too delicate a nature for us to touch upon.

² This refers to Thomas Sherlock (1678-1761), Church of England Bishop of London from 1748 to 1761.

4-: From a letter by ‘Oedipus’, published in The Kentish Gazette (Canterbury, Kent, England) of Saturday 15^th July 1769:

POETS CORNER.
To the PRINTER.

SIR,
I Never was an admirer of mysterious writing, and as mistakes of a dangerous nature frequently arise from studied obscurity, I think every one deserves of the public who clears up such dark compositions. This was the motive for the following attempt to give the true meaning of Mr. Gray’s Installation Ode; for it is plain something more is meant than meets the eye. For if we understand it literally, it is all a pack of lies and nonsense.

5-: From The Praises of Poetry. A Poem (London: Printed for W. Owen, 1775), by the English lawyer and author Capel Lofft (1751-1824):

For not the Cretan Jove,
His birth and the wild legends of his love,
Contented thy rapacious mind:
Though these involv’d in allegoric veil
A deeper sense than meets the eye conceal:
Something far greater didst thou see;
Something beyond the deep obscurity.

6-: From the opening lines of Strictures on a Sermon, entitled, The Principles of the Revolution vindicated; Preached before the University of Cambridge, on Wednesday, May 29^th, 1776, by Richard Watson, D.D. F.R.S. Regius Professor of Divinity in that University. In a Letter to a Friend (Cambridge: Printed and sold by J. Woodyer, [1776]), by the English author William Stevens (1732-1807):

Dear Sir,
WE have lately had a very curious Discourse preached and published here by Dr. Watson, Regius Professor of Divinity in this University, which I take the liberty to send you, with a few Strictures on it. There is something singularly happy in the choice of the subject for the day. The Dr. you must know, is your man for a Word in Season; he pitched on the 29^th of May, the day of the Restoration, to vindicate before the University the principles of the Revolution. Perhaps ill-natured people may insinuate, that by this, more was meant than meets the eye; that the Dr. had in view a complete Revolution, a revolving to the point from which we set out; but I dare say it was no such thing.

7-: From the following note, appended to a letter “To the Free Burgesses of Newcastle”, dated Newcastle-upon-Tyne, Thursday 31^st August 1780, by ‘An Indignant Burgess’, published in The Newcastle Chronicle (Newcastle-upon-Tyne, Northumberland, England) of Saturday 9^th September 1780:

Either by the writer’s desire, or the little Editor’s order, I shall suppose the Newcastle Burgesses are respectably placed in the same page with the HUE and CRY, after Thieves and Vagabonds!—There’s more meaning in this little circumstance than meets the eye.