In the forground is a pair of Jai Prakâsh Yantra (Armillary Sphere Instruments)
and in the backgound is two Râm Yantras (Altitude/Azimuth Instruments).
The Delhi Jantar Mantar at the time when G.R. Kaye researched in 1915.
Both photos were taken from the top of the Brihat Samrât Yantra
from the same angle with an interval of 80 years.