It is to be observed that "angling" is the name given to fishing by people who can't fish. Stephen Leacock
Remember this-that there is a proper dignity and proportion to be observed in the performance of every act of life. Marcus Aurelius
Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed. Albert Einstein
But people themselves alter so much, that there is something new to be observed in them for ever. Jane Austen
Aristocrats might shrug, but commoners, dreading any collapse of the social order, wanted the rules of behavior to be observed. Robert Silverberg
The proper form of economy must be observed in building houses for each and every class. Vitruvius