Kalpa

The first bhava, or house, is the rising sign itself, the sign on the eastern horizon at the moment of birth, called the Lagna. Every other house is counted from it. In the Brihat Jataka a house is a whole sign, so house 1 covers the full 30 degrees of the Lagna sign, and the calculator follows that rule.

Iyer's list for this house in his translation of the Brihat Jataka reads body, fame and limbs, and the book names the sign of this place Kalpa, power. The quoted verse comes from chapter 11 of the Brihat Parashara Hora Shastra, as typed on Wikisource from an edition no one has identified. As we read it, it speaks of the body, the form, knowledge, color, strength and weakness, comfort and sorrow, and nature. The first house is also one of the four kendras, the angles, which the book counts as naturally strong.

Varahamihira says the Lagna becomes powerful when its lord, Jupiter or Mercury sits in it or looks at it, and he says other planets do not do this. Iyer's introduction goes further and calls the Lagna a basic factor in the book's method. The book also uses the word Hora for the rising sign.