Rule of thumb is an approximate method for doing something, based on practical experience rather than theory. This usage of the phrase can be traced back to the 17th century and has been associated with various trades where quantities were measured by comparison to the width or length of a thumb. A modern folk etymology holds that the phrase is derived from the maximum width of a stick allowed for wife-beating under English common law, but no such law ever existed. This belief may have originated in a rumored statement by 18th-century judge Sir Francis Buller that a man may beat his wife with a stick no wider than his thumb. The rumor produced numerous jokes and satirical cartoons at Buller's expense, but there is no record that he made such a statement. English jurist Sir William Blackstone wrote in his Commentaries on the Laws of England of an "old law" that once allowed "moderate" beatings by husbands, but he did not mention thumbs or any specific implements. Wife-beating has been officially
La regla del pulgar es un método aproximado para hacer algo, basado en la experiencia práctica en lugar de la teoría. Este uso de la frase se puede rastrear hasta el siglo XVII y se ha asociado con diversos negocios donde las cantidades se medían en comparación con la anchura o la longitud de un pulgar. Una etimología popular moderna sostiene que la frase se deriva de la anchura máxima de un bastón permitido para golpear a la esposa bajo la ley común inglesa, pero no hay ningún registro de que haya existido tal ley. Esta creencia puede haberse originado en una declaración rumorosa por el juez del siglo XVIII Sir Francis Buller de que un hombre puede golpear a su esposa con un bastón no más ancho que su pulgar. El rumor produjo numerosas bromas y dibujos animados satíricos a expensas de Buller, pero no hay registro de que hubiese hecho tal declaración.