Anna Laetitia Barbauld - Riddle #2

This creature, though extremely thin,
In shape is almost square;
Has many heads, on which ne'er grew
One single lock of hair.
Yet several of their tribe there are,
Whose case you must bewail,
Of whom in truth it may be said
They 've neither head nor tail.
In purer times, ere vice prevailed,
They met with due regard,
The wholesome counsels that they gave,
With reverence were heard.

To marriages and funerals
Their presence added grace,
And though the king himself were by,
They took the highest place.
Their business is to stir up men
A constant watch to keep;
Instead of which,—O sad reverse,—
They make them fall asleep.
Not so in former times it was,
Howe'er it came to pass;
Though they their company ne'er left
Till empty was the glass.
The moderns can't be charged with this,
But may their foes defy,
To prove such practices on them,
Though they 're extremely dry.

Anna Laetitia Barbauld

http://www.poemhunter.com/poem/riddle-2-3/