On a finger of his right hand he wore a diamond ring, one set with a ruby, or emerald

Fascinating story about Tipu’s Golden Box. I quote:

Munshi Qasim, in his account of Tipu's court, recorded that Tipu daily consulted his astrologers about the state of the stars and every Saturday unfailingly, he made an offering to the seven stars of different kinds of grain, of an iron pan full of sesame oil, a blue cap and coat, one black sheep and some money. On a finger of his right hand he wore a diamond ring, one set with a ruby, or emerald, varying every day in colour according to the course of the seven stars. The name of Tipu's astrologer is given as En Enkut Rumna.

Tipu was a bibliophile as well. His library has been described as:

Tipu maintained a superb and varied library of more than 200 volumes. They were catalogued by Charles Stewart in 1809 and published as A Descriptive Catalogue of the Oriental Library of the Late Tippoo Sultan of Mysore, Cambridge University Press, 1809.
Stewart wrote "The library contained many curious and interesting manuscripts of which the following is a summary; Koran: 44 volumes; commentaries on Koran: 41; prayers: 35; traditions: 46; theology: 46; sufism (mystic writings): 115; ethics: 24; jurisprudence: 95; arts and sciences: 19; philosophy: 54; astronomy: 80; mathematics: 7; physics: 62; philology: 45; lexicography: 29; history: 118; letters: 53; poetry: 261; Hindi and Deccani poetry: 23; Hindi and Deccani prose: 4; Turkish prose: 2; fables: 18"
Stewart lists Tipu's books on mathematics:
Persian books:
1. Resaleh Ilmi Hesab, Thin Quarto, Common Hand, A useful treatise on arithmatic, according to the Hindu system, Author unknown
2. Muntekhab Ilmi, Quarto, Common Hand, A very excellent Treatise on Mathematics and Geometry, According to the Indian System, Author, Lutif Allah, Engineer of Dhely (sic.), A.D. 1681
3. Kholaseh a Hesab, A Treatise on Mathematics, written both in Persian and Arabic, Author, Molana Baha Addeen
Arabic Books:
4. Tahrir Aklydis, Octavo, Niskh (sic.) Character, The Elements of Euclid, Translated from the Greek by Ishak Ben Honain
(Euclid discusses the Platonic Solids in Elements)
5. Shereh Shems al Manury, Octavo, Niskh (sic.) Character
A Commentary on the Shems al Manury (or 'Sun of Truth'), A very celebrated Work on Geometry and Mathematics, Author, Muhammed Ben Ahmed al Jafery
6-7. Two volumes, Octavo, Niskh (sic.) Character, Two Esteemed Treatises on Geometry and Arithmetic, Authors unknown
On p.97, in the section on Arts and Sciences, Stewart adds the note: "It appears that Tippoo was an Encourager and Patron of the Arts; and it is stated that Forty Five Books on different Sciences were either compiled, or translated from different languages, under his immediate Inspection or Auspices. It is probable that some of our unfortunate Countrymen, who were so long detained in Captivity, and had thereby acquired a Knowledge of the Dekhany Languages, assisted him in these Pursuits."

But the best is his Gold Icosahedron Box.

"This twenty-sided gold box was found in the treasury of Tippoo Sahib at the taking of Seringapatam on May 4, 1799, and was given by General Robert Bell of the Honorable E. India Co's Madras Artillery, who was one of the Commissioners of Prizes on that occasion, to his friend Sir Charles Hopkinson, from whom it descended to his Great Nephew Hans William Sotheby, first Husband of Charlotte Cornish, whose second Husband, Ingram Bywater, sometimes Regius Professor of Greek in the University of Oxford, bequeathed it to Charles Francis Bell, a great-grandson of the above mentioned General Robert Bell, December 1914"