An ear pressed to the keyhole!

Eavesdropping is as old as time.

Kautilya better known as Chanakya has devoted a section on spying in his political treatise Arthasashtra,written by him in the 3rd cetury BC.
The role of a spy was , just as it is now,to gather information from the ruled without their knowledge.

There was no written constitution then . The members of the constituent assembly of India[ my maternal grand father M.Ananthasayanam Ayengar was one of them] who reverently framed the fundamental rights were yet to be born .To him [ my grand father] the Constitution of India was a sacred document and he cherished it dearly and accorded it an exalted position in his life that was second only to the great respect he had towards the Vedas, Upanishads and the Bhagwat gita and the unshakeable faith he reposed in them !
The fundamental right to ,'life and liberty' which has been interpreted to include the 'right to privacy' by the Supreme court of India was unheard of, way back in ancient India.

Chandragupta Maurya the first historical emperor of India, under the able guidance of his mentor and Prime minister Chanakya eavesdropped on his subjects!

He did so with the intention of bringing criminals and wrong doers to justice and to uphold the laws of the land.