The London Lounge

In [i]The gentleman's art of dressing with economy[/i] (London, 1876), 'A Lounger at The Clubs' wrote:
For trousers to fit well, it is of first importance that they be well up in the fork, and reach right down to the ground. Short-legged trousers defeat all attempt at trying to appear well dressed. If muddy, turn them up (fortunately it is the fashion to do so nowadays), and have the back edge round the heel inside bound with a slip of morocco leather, half inch deep, which should be flush with the bottom of the legs. This prevents their cutting with the ground; for in this case they cannot be let down should they shrink in wear.

Trousers should be cut to fall straight from the knee (plumb-line), with a slight spring over boot. The width over boot is invariably one inch and a half wider than knee measurement. Most tailors fail to hit off the just milieu at the termination of their trousers, and make them either too gaitery, like the bottom of a caraffe, else slope them away horsey, or in ostler fashion. [...]

One word about material, another about patterns. Avoid soft nappy cloths: the pile quickly wears off, and the trousers look threadbare. Choose firm, strong tweeds. Some are like pinwire, and wear practically for ever.

In patterns shun checks, plaids, and chessboard devices. Never order any material so prononcé that you would know it again. Stripes in long parallel lines are to be avoided; when the knees get ever so slightly baggy, the break in continuity of the lines draws attention, and makes your pantaloons, though only out of shape, look shabby. Pepper-and-salt, light and dark brown, and all grey mixtures devoid of any decided pattern, will be found most serviceable, and are always fashionable. [...]