Jantar Mantar , Jaipur

Vrihat Samrat Yantra (Equinoctial Sundial)

• This is a Sun Dial that can give the time to an accuracy of 2 seconds. 
• Planned around 1732, completed around 1735. 
• Repaired in 1901–1902 with plaster scales of quadrants redrawn and gnomon edges engraved in red stone. 
• Scales surfaced with marble in 1945. 
• Red sandstone lining replaced the earlier masonry plaster surface after 1969 (Volwahsen, 2001) 
• Lime plastered in 2007 and storm water collection was channelised.

Sasthamsa Yantra (60 deg. Meridian Chamber)

• It is used for measuring the declination and zenith distance of Sun 
• Constructed with the Vrihat Samrat Yantra 
• Initially, scales inscribed on smooth lime plaster surface, as also followed in 1901-1902 restoration. Marble scale introduced later 
• Pointed arches on surface of the eastern Sasthamsa filled up and affixed with doors. This infill removed in 2007 restoration to reveal the original arches

Jai Prakash Yantra (Hemispherical Inst.)

• These are twin hemispherical bowl instruments, each one is a reflection of sky above 
• Constructed under the supervision of Maharaja Sawai Jai Singh II (before 1743) 
• During later restorations, ten staircases leading to the underground rooms and corridors were walled up 
• Scales of plaster replaced with marble ones, after 1945 or in 1901-1902 
• Plinth protection in stone re-laid during 2007 restoration

Nadivalaya Yantra (Equinoctial Dial)

• Helps in determining the time 
•Only northern part (Uttari Gola) built originally, southern part and the storage chamber added before the reign of Maharaja Pratap Singh, when the whole building was rebuilt (1771) 
•Inscription on plaque on southern plate mentions date of second restoration to be January 25, 1771. First restoration possibly under the supervision of Sawai Madho Singh 
•In 2007, damaged calibrations were refilled with lead and the structure was plastered with lime. The access door was replaced