Lewis & Short

capsŭla, ae, f. dim. [capsa], a small box or chest, Fab. Pictor. ap. Gell. 10, 15, 14; Cat. 68, 36; Plin. 30, 11, 30, § 102.
Hence, homo de capsulā, one who is excessively neat, nice: juvenes barbā et comā nitidi, de capsulā toti, quite from the bandbox, Sen. Ep. 115, 2.