To sit gracefully one should not perch stiffly on the edge of a straight chair, nor sprawl at lenght in an easy one.
The perfect position is one that is easy, but dignified. In other days, no lady of dignity ever crossed her knees, held her hands on her lips, or twisted herself sideways, or even leaned back in the chair!
Today all these things are done and the only etiquette left is on the subject of how not to exaggerate them.
No lady should cross her knees so that her skirt go up to or above them; neither should her foot be thrust out so that her toes are at knee level.
An arm a-kimbo is not a graceful attitude, nor is a twisted spin!
Everyone, of course, leans against a chair back, except in a box at the opera and in a ballroom, but a lady should never throw herself almost at full lenght in a reclining chair or on a wide sofa when she is out in public.
She may lean back, of course, and easily; her hands relaxed in her lap, her knees together, or if crossed, her foot must not be thrust forward so as to leave a space between the heel and her other ankle.
This is, however, not so much a rule of etiquette as a question of beauty and fitness.
Emily Post’s Etiquette