Which preposition to use with mayoress

at Occurrences 1%

Visited the Lady Mayoress at the Mansion House, and felt quite at ease.

in Occurrences 1%

The Duchess of Richmond was a Lady Mayoress in the time of James I.; and Lord Delawarr, Queen Elizabeth's porter, from a picture in the guard-chamber at Kensington: they were admirable masks.

Which preposition to use with  mayoress