Laghumānasa

Laghu-mānasa (c. 932 CE) is a Sanskrit-language text on astronomy by the Indian astronomer Mañjula. It is a "karana" text containing simple rules for astronomical calculations, aimed at panchanga-makers. It remained highly popular across a vast region of present-day India for several years: the first pre-modern commentary on it was written in Kashmir in 958, and the last one was written in 1732 in Kerala.
Date and authorship.
"Laghu-mānasa" is the only surviving work of Mañjula, whose geographic location is not known. Mañjula adopted 10 March 932 CE (Saturday noon of Chaitra 1, Shaka 854) as the epoch of calculation in text, which suggests that he started composing the text sometime in 932 CE.
According to Surya-deva Yajva's commentary on the text, Mañjula studied several works on astronomy, and summarized them in an earlier work called "Laghu-mānasa". He asked one of his pupils to take a copy of the work to the local king. The pupil did so, but took credit for writing the work. When Mañjula later visited the king, he asked the king to test him and the pupil by making them write another text on the same day, in the king's custody. Mañjula then wrote the present-day "Laghu-mānasa", while the pupil was unable to write anything. The king banished the pupil, rewarded Mañjula, and popularized the latest "Laghu-mānasa".
Content.
"Laghu-mānasa", also called "Laghumanāsam", is a "karana" text, that is, a work containing short and simple rules for astronomical calculations aimed to help the panchanga-makers. It is the smallest "karana" text of classical Indian astronomy: the main text contains 60 "anushtubh"-metre verses that provide the rules, plus an additional 5 "arya"-metre verses that provide the epochal constants required for the calculations. According to commentator Surya-deva Yajva, Mañjula wrote the additional verses in the "arya" metre so as not to mix up the constants with the main text, and to remind the reader to revise the consonants every 100 years.
The text provides much of the planetary model information known to the contemporary Indian astronomers, and appears to derive information from earlier sources including Aryabhata's various works (c. 500), Brahmagupta's "Brahma-sphuta-siddhanta" (c. 628 CE), and Lata-deva's "Surya-siddhanta" (6th century).
Chapters.
Different commentators divide the text into chapters in different ways. The critical edition by K.S. Shukla divides the text into 9 chapters (Sanskrit names in IAST):
Pratashti-dhara divides the text into 8 chapters:
Surya-deva Yajva divides the text into 4 chapters, sub-dividing the first chapter into 3 sections:
Parameshvara's classification is almost same as that of Surya-deva Yajva, but he titles the fourth chapter "Saṃkīrṇādhikāra". He includes an additional verse (53' in Shukla's critical edition), but states that some people omit it.
Yallaya and Bhūdhara divide the text into 8 chapters:
Legacy.
"Laghu-mānasa" provides short and simple calendaric methods, generally not known to the earlier Indian astronomers, and thus, became an important work in the Indian astronomy. It is the earliest known text to use the process of differentiation in finding the velocity of a planet. It also the earliest known Indian text to outline the lunar correction comprising evection (commentator Yallaya attributes this correction to the "Vateshvara-siddhanta", but the surviving manuscripts of that work do not mention it). Unlike earlier astronomers, Mañjula rejects the theory of oscillatory motion of the equinoxes, and recommends a progressive precessional motion.
"Laghu-mānasa" was popular across a vast area of present-day India, as evident from the commentaries written on it. Commentators on the work include Prashastidhara of Kashmir, Surya-deva Yajva of Gangai-konda-Cholapuram (Tamil Nadu); Yallaya of Skanda-someshvara (Andhra Pradesh); Parameshvara of Alattur (Kerala), Bhudhara of Kampilya (Uttar Pradesh), and an anonymous commentator of Karnata-desha (Karnataka). Writers from several other places adopted or referred to Mañjula's work; for example, Bhoja of Malwa (Madhya Pradesh), Dashabala of Gujarat, Bhaskara II of Bida (Maharashtra), and Shri-datta of Nepala.
The work was especially popular in present-day Andhra Pradesh and Kerala, as late as until the 17th-18th centuries, as attested by the composition of Telugu (1695 CE) and Malayalam (1732 CE) commentaries there.
Commentaries and derivative texts.
Historical commentaries on the text include:
The following historical works are derived from the "Laghu-mānasa":
"Laghu-mānasaritya Surya-chandra-grahananayanam" is a 16th-century text based on "Laghu-mānasa"
The following texts adopt Mañjula's rules:
Critical editions.
A printed edition with commentary of Parameshvara was published as part of the Ānandāśrama Sanskrit Series from Pune in 1944. An English translation by N.K. Majumdar was published from Calcutta in 1951.
Kripa Shankar Shukla's critical edition of the text with an English translation and notes was published as a supplement to the Volume 25 of the "Indian Journal of History of Science" (1990) by the Indian National Science Academy, New Delhi. It was based on 11 manuscripts, available at Government Oriental Library (Mysore; now Oriental Research Institute), Government Oriental Manuscripts Library (Madras), and Sampurnananda Sanskrit University Library (Varanasi).